diff --git a/src/sio3pack/packages/package/model.py b/src/sio3pack/packages/package/model.py
index cea7afd..85972e1 100644
--- a/src/sio3pack/packages/package/model.py
+++ b/src/sio3pack/packages/package/model.py
@@ -4,8 +4,6 @@
 from sio3pack.graph.graph import Graph
 from sio3pack.packages.exceptions import UnknownPackageType
 from sio3pack.test.test import Test
-
-from sio3pack.packages import all_packages
 from sio3pack.utils.archive import Archive
 from sio3pack.utils.classinit import RegisteredSubclassesBase
 
@@ -14,6 +12,7 @@ class Package(RegisteredSubclassesBase):
     """
     Base class for all packages.
     """
+
     abstract = True
 
     def __init__(self, file: File):
diff --git a/src/sio3pack/packages/sinolpack/enums.py b/src/sio3pack/packages/sinolpack/enums.py
index 6f81e47..0f44533 100644
--- a/src/sio3pack/packages/sinolpack/enums.py
+++ b/src/sio3pack/packages/sinolpack/enums.py
@@ -8,10 +8,10 @@ class ModelSolutionKind(Enum):
 
     @classmethod
     def from_regex(cls, group):
-        if group == '':
+        if group == "":
             return cls.NORMAL
-        if group == 's':
+        if group == "s":
             return cls.SLOW
-        if group == 'b':
+        if group == "b":
             return cls.INCORRECT
         raise ValueError(f"Invalid model solution kind: {group}")
diff --git a/src/sio3pack/packages/sinolpack/model.py b/src/sio3pack/packages/sinolpack/model.py
index 374f5e1..65fb3b8 100644
--- a/src/sio3pack/packages/sinolpack/model.py
+++ b/src/sio3pack/packages/sinolpack/model.py
@@ -1,9 +1,9 @@
-import json
 import os
 import re
-import yaml
 import tempfile
 
+import yaml
+
 from sio3pack.files.file import File
 from sio3pack.graph.graph import Graph
 from sio3pack.graph.graph_manager import GraphManager
@@ -26,7 +26,7 @@ def _find_main_dir(cls, archive: Archive) -> str | None:
         toplevel_dirs = list(set(f.split(os.sep)[0] for f in dirs))
         problem_dirs = []
         for dir in toplevel_dirs:
-            for required_subdir in ('in', 'out'):
+            for required_subdir in ("in", "out"):
                 if all(f.split(os.sep)[:2] != [dir, required_subdir] for f in dirs):
                     break
             else:
@@ -68,7 +68,7 @@ def __init__(self, file: File, django_settings=None):
             self.rootdir = file.path
 
         try:
-            graph_file = self.get_in_root('graph.json')
+            graph_file = self.get_in_root("graph.json")
             self.graph_manager = GraphManager.from_file(graph_file)
         except FileNotFoundError:
             self.has_custom_graph = False
@@ -76,12 +76,16 @@ def __init__(self, file: File, django_settings=None):
         self.django_settings = django_settings
 
     def _default_graph_manager(self) -> GraphManager:
-        return GraphManager({
-            "unpack": Graph.from_dict({
-                "name": "unpack",
-                # ...
-            })
-        })
+        return GraphManager(
+            {
+                "unpack": Graph.from_dict(
+                    {
+                        "name": "unpack",
+                        # ...
+                    }
+                )
+            }
+        )
 
     def _get_from_django_settings(self, key: str, default=None):
         if self.django_settings is None:
@@ -92,7 +96,7 @@ def get_doc_dir(self) -> str:
         """
         Returns the path to the directory containing the problem's documents.
         """
-        return os.path.join(self.rootdir, 'doc')
+        return os.path.join(self.rootdir, "doc")
 
     def get_in_doc_dir(self, filename: str) -> File:
         """
@@ -110,7 +114,7 @@ def get_prog_dir(self) -> str:
         """
         Returns the path to the directory containing the problem's program files.
         """
-        return os.path.join(self.rootdir, 'prog')
+        return os.path.join(self.rootdir, "prog")
 
     def get_in_prog_dir(self, filename: str) -> File:
         """
@@ -122,7 +126,7 @@ def get_attachments_dir(self) -> str:
         """
         Returns the path to the directory containing the problem's attachments.
         """
-        return os.path.join(self.rootdir, 'attachments')
+        return os.path.join(self.rootdir, "attachments")
 
     def _process_package(self):
         self._process_config_yml()
@@ -141,7 +145,7 @@ def _process_config_yml(self):
         Process the config.yml file. If it exists, it will be loaded into the config attribute.
         """
         try:
-            config = self.get_in_root('config.yml')
+            config = self.get_in_root("config.yml")
             self.config = yaml.safe_load(config.read())
         except FileNotFoundError:
             self.config = {}
@@ -155,14 +159,14 @@ def _detect_full_name(self):
         Example of how the ``title`` tag may look like:
         \title{A problem}
         """
-        if 'title' in self.config:
-            self.full_name = self.config['title']
+        if "title" in self.config:
+            self.full_name = self.config["title"]
             return
 
         try:
-            source = self.get_in_doc_dir(self.short_name + 'zad.tex')
+            source = self.get_in_doc_dir(self.short_name + "zad.tex")
             text = source.read()
-            r = re.search(r'^[^%]*\\title{(.+)}', text, re.MULTILINE)
+            r = re.search(r"^[^%]*\\title{(.+)}", text, re.MULTILINE)
             if r is not None:
                 self.full_name = r.group(1)
         except FileNotFoundError:
@@ -174,8 +178,8 @@ def _detect_full_name_translations(self):
         two-letter language code defined in ``settings.py``), if any such key is given.
         """
         self.lang_titles = {}
-        for lang_code, lang in self._get_from_django_settings('LANGUAGES', [('en', 'English')]):
-            key = 'title_%s' % lang_code
+        for lang_code, lang in self._get_from_django_settings("LANGUAGES", [("en", "English")]):
+            key = "title_%s" % lang_code
             if key in self.config:
                 self.lang_titles[lang_code] = self.config[key]
 
@@ -184,8 +188,7 @@ def get_submittable_extensions(self):
         Returns a list of extensions that are submittable.
         """
         return self.config.get(
-            'submittable_langs',
-            self._get_from_django_settings('SUBMITTABLE_LANGUAGES', ['c', 'cpp', 'cxx', 'py'])
+            "submittable_langs", self._get_from_django_settings("SUBMITTABLE_LANGUAGES", ["c", "cpp", "cxx", "py"])
         )
 
     def get_model_solution_regex(self):
@@ -193,7 +196,7 @@ def get_model_solution_regex(self):
         Returns the regex used to determine model solutions.
         """
         extensions = self.get_submittable_extensions()
-        return rf'^{self.short_name}[0-9]*([bs]?)[0-9]*(_.*)?\.(' + '|'.join(extensions) + ')'
+        return rf"^{self.short_name}[0-9]*([bs]?)[0-9]*(_.*)?\.(" + "|".join(extensions) + ")"
 
     def _get_model_solutions(self) -> list[tuple[ModelSolutionKind, str]]:
         """
@@ -208,13 +211,17 @@ def _get_model_solutions(self) -> list[tuple[ModelSolutionKind, str]]:
 
         return model_solutions
 
-    def sort_model_solutions(self, model_solutions: list[tuple[ModelSolutionKind, str]]) -> list[tuple[ModelSolutionKind, str]]:
+    def sort_model_solutions(
+        self, model_solutions: list[tuple[ModelSolutionKind, str]]
+    ) -> list[tuple[ModelSolutionKind, str]]:
         """
         Sorts model solutions by kind.
         """
+
         def sort_key(model_solution):
             kind, name = model_solution
             return kind.value, naturalsort_key(name[: name.index(".")])
+
         return list(sorted(model_solutions, key=sort_key))
 
     def _process_prog_files(self):
@@ -233,13 +240,17 @@ def _process_prog_files(self):
             self.additional_files = self.graph_manager.get_prog_files()
         else:
             self.additional_files = []
-            self.additional_files.extend(self.config.get('extra_compilation_files', []))
-            self.additional_files.extend(self.config.get('extra_execution_files', []))
+            self.additional_files.extend(self.config.get("extra_compilation_files", []))
+            self.additional_files.extend(self.config.get("extra_execution_files", []))
             extensions = self.get_submittable_extensions()
             self.special_files: dict[str, bool] = {}
-            for file in ('ingen', 'inwer', 'soc', 'chk'):
+            for file in ("ingen", "inwer", "soc", "chk"):
                 try:
-                    self.additional_files.append(File.get_file_matching_extension(self.get_prog_dir(), self.short_name + file, extensions).filename)
+                    self.additional_files.append(
+                        File.get_file_matching_extension(
+                            self.get_prog_dir(), self.short_name + file, extensions
+                        ).filename
+                    )
                     self.special_files[file] = True
                 except FileNotFoundError:
                     self.special_files[file] = False
@@ -256,12 +267,14 @@ def _process_statements(self):
         if not os.path.exists(docdir):
             return
 
-        lang_prefs = [''] + ['-' + l[0] for l in self._get_from_django_settings('LANGUAGES', [('en', 'English'), ('pl', 'Polish')])]
+        lang_prefs = [""] + [
+            "-" + l[0] for l in self._get_from_django_settings("LANGUAGES", [("en", "English"), ("pl", "Polish")])
+        ]
 
         self.lang_statements = {}
         for lang in lang_prefs:
             try:
-                htmlzipfile = self.get_in_doc_dir(self.short_name + 'zad' + lang + '.html.zip')
+                htmlzipfile = self.get_in_doc_dir(self.short_name + "zad" + lang + ".html.zip")
                 # TODO: what to do with html?
                 # if self._html_disallowed():
                 #     raise ProblemPackageError(
@@ -281,8 +294,8 @@ def _process_statements(self):
                 pass
 
             try:
-                pdffile = self.get_in_doc_dir(self.short_name + 'zad' + lang + '.pdf')
-                if lang == '':
+                pdffile = self.get_in_doc_dir(self.short_name + "zad" + lang + ".pdf")
+                if lang == "":
                     self.statement = pdffile
                 else:
                     self.lang_statements[lang[1:]] = pdffile
@@ -290,9 +303,7 @@ def _process_statements(self):
                 pass
 
     def _process_attachments(self):
-        """
-
-        """
+        """ """
         attachments_dir = self.get_attachments_dir()
         if not os.path.isdir(attachments_dir):
             return
@@ -305,7 +316,7 @@ def _process_attachments(self):
     def get_unpack_graph(self) -> GraphOperation | None:
         try:
             return GraphOperation(
-                self.graph_manager.get('unpack'),
+                self.graph_manager.get("unpack"),
                 True,
                 self._unpack_return_data,
             )
diff --git a/src/sio3pack/util.py b/src/sio3pack/util.py
index 0bc26a3..855f96f 100644
--- a/src/sio3pack/util.py
+++ b/src/sio3pack/util.py
@@ -1,9 +1,6 @@
 import re
-import tarfile
-import zipfile
 
-from sio3pack.files.file import File
 
 def naturalsort_key(key):
     convert = lambda text: int(text) if text.isdigit() else text
-    return [convert(c) for c in re.split('([0-9]+)', key)]
+    return [convert(c) for c in re.split("([0-9]+)", key)]
diff --git a/src/sio3pack/utils/archive.py b/src/sio3pack/utils/archive.py
index 1a86127..847eb81 100644
--- a/src/sio3pack/utils/archive.py
+++ b/src/sio3pack/utils/archive.py
@@ -41,7 +41,7 @@ class UnsafeArchive(ArchiveException):
     """
 
 
-def extract(path, to_path='', ext='', **kwargs):
+def extract(path, to_path="", ext="", **kwargs):
     """
     Unpack the tar or zip file at the specified path to the directory
     specified by to_path.
@@ -54,7 +54,7 @@ class Archive(object):
     The external API class that encapsulates an archive implementation.
     """
 
-    def __init__(self, file, ext=''):
+    def __init__(self, file, ext=""):
         """
         Arguments:
         * 'file' can be a string path to a file or a file-like object.
@@ -66,7 +66,7 @@ def __init__(self, file, ext=''):
         self._archive = self._archive_cls(self.filename, ext=ext)(self.filename)
 
     @staticmethod
-    def _archive_cls(file, ext=''):
+    def _archive_cls(file, ext=""):
         """
         Return the proper Archive implementation class, based on the file type.
         """
@@ -78,9 +78,7 @@ def _archive_cls(file, ext=''):
             try:
                 filename = file.name
             except AttributeError:
-                raise UnrecognizedArchiveFormat(
-                    "File object not a recognized archive format."
-                )
+                raise UnrecognizedArchiveFormat("File object not a recognized archive format.")
         lookup_filename = filename + ext
         base, tail_ext = os.path.splitext(lookup_filename.lower())
         cls = extension_map.get(tail_ext)
@@ -88,9 +86,7 @@ def _archive_cls(file, ext=''):
             base, ext = os.path.splitext(base)
             cls = extension_map.get(ext)
         if not cls:
-            raise UnrecognizedArchiveFormat(
-                "Path not a recognized archive format: %s" % filename
-            )
+            raise UnrecognizedArchiveFormat("Path not a recognized archive format: %s" % filename)
         return cls
 
     @classmethod
@@ -152,10 +148,10 @@ def _extract(self, to_path):
         """
         self._archive.extractall(to_path)
 
-    def extract(self, to_path='', method='safe'):
-        if method == 'safe':
+    def extract(self, to_path="", method="safe"):
+        if method == "safe":
             self.check_files(to_path)
-        elif method == 'insecure':
+        elif method == "insecure":
             pass
         else:
             raise ValueError("Invalid method option")
@@ -175,8 +171,7 @@ def check_files(self, to_path=None):
             extract_path = os.path.normpath(os.path.realpath(extract_path))
             if not extract_path.startswith(target_path):
                 raise UnsafeArchive(
-                    "Archive member destination is outside the target"
-                    " directory.  member: %s" % filename
+                    "Archive member destination is outside the target" " directory.  member: %s" % filename
                 )
 
 
@@ -189,14 +184,10 @@ def __init__(self, file):
             self._archive = tarfile.open(fileobj=file)
 
     def filenames(self):
-        return [
-            tarinfo.name for tarinfo in self._archive.getmembers() if tarinfo.isfile()
-        ]
+        return [tarinfo.name for tarinfo in self._archive.getmembers() if tarinfo.isfile()]
 
     def dirnames(self):
-        return [
-            tarinfo.name for tarinfo in self._archive.getmembers() if tarinfo.isdir()
-        ]
+        return [tarinfo.name for tarinfo in self._archive.getmembers() if tarinfo.isdir()]
 
     def extracted_size(self):
         total = 0
@@ -226,25 +217,17 @@ def extracted_size(self):
         return total
 
     def filenames(self):
-        return [
-            zipinfo.filename
-            for zipinfo in self._archive.infolist()
-            if not zipinfo.is_dir()
-        ]
+        return [zipinfo.filename for zipinfo in self._archive.infolist() if not zipinfo.is_dir()]
 
     def dirnames(self):
-        return [
-            zipinfo.filename
-            for zipinfo in self._archive.infolist()
-            if zipinfo.is_dir()
-        ]
+        return [zipinfo.filename for zipinfo in self._archive.infolist() if zipinfo.is_dir()]
 
 
 extension_map = {
-    '.tar': TarArchive,
-    '.tar.bz2': TarArchive,
-    '.tar.gz': TarArchive,
-    '.tgz': TarArchive,
-    '.tz2': TarArchive,
-    '.zip': ZipArchive,
+    ".tar": TarArchive,
+    ".tar.bz2": TarArchive,
+    ".tar.gz": TarArchive,
+    ".tgz": TarArchive,
+    ".tz2": TarArchive,
+    ".zip": ZipArchive,
 }
diff --git a/src/sio3pack/utils/classinit.py b/src/sio3pack/utils/classinit.py
index 5330916..a1356b4 100644
--- a/src/sio3pack/utils/classinit.py
+++ b/src/sio3pack/utils/classinit.py
@@ -1,5 +1,6 @@
 # From oioioi/base/utils/__init__.py
 
+
 class ClassInitMeta(type):
     """Meta class triggering __classinit__ on class intialization."""
 
@@ -56,28 +57,24 @@ class RegisteredSubclassesBase(ClassInitBase):
 
     @classmethod
     def __classinit__(cls):
-        this_cls = globals().get('RegisteredSubclassesBase', cls)
+        this_cls = globals().get("RegisteredSubclassesBase", cls)
         super(this_cls, cls).__classinit__()
         if this_cls is cls:
             # This is RegisteredSubclassesBase class.
             return
 
-        assert 'subclasses' not in cls.__dict__, (
-            '%s defines attribute subclasses, but has '
-            'RegisteredSubclassesMeta metaclass' % (cls,)
-        )
+        assert (
+            "subclasses" not in cls.__dict__
+        ), "%s defines attribute subclasses, but has " "RegisteredSubclassesMeta metaclass" % (cls,)
         cls.subclasses = []
-        cls.abstract = cls.__dict__.get('abstract', False)
+        cls.abstract = cls.__dict__.get("abstract", False)
 
         def find_superclass(cls):
             superclasses = [c for c in cls.__bases__ if issubclass(c, this_cls)]
             if not superclasses:
                 return None
             if len(superclasses) > 1:
-                raise AssertionError(
-                    '%s derives from more than one '
-                    'RegisteredSubclassesBase' % (cls.__name__,)
-                )
+                raise AssertionError("%s derives from more than one " "RegisteredSubclassesBase" % (cls.__name__,))
             superclass = superclasses[0]
             return superclass
 
diff --git a/tests/fixtures.py b/tests/fixtures.py
index 5da0f01..7e31c57 100644
--- a/tests/fixtures.py
+++ b/tests/fixtures.py
@@ -24,9 +24,9 @@ def _tar_archive(dir, dest, compression=None):
     Create a tar archive of the specified directory.
     """
     if compression is None:
-        mode = 'w'
+        mode = "w"
     else:
-        mode = f'w:{compression}'
+        mode = f"w:{compression}"
     with tarfile.open(dest, mode) as tar:
         tar.add(dir, arcname=os.path.basename(dir))
 
@@ -35,7 +35,7 @@ def _zip_archive(dir, dest):
     """
     Create a zip archive of the specified directory.
     """
-    with zipfile.ZipFile(dest, 'w') as zip:
+    with zipfile.ZipFile(dest, "w") as zip:
         for root, dirs, files in os.walk(dir):
             for file in files:
                 zip.write(os.path.join(root, file), os.path.relpath(os.path.join(root, file), dir))
@@ -70,6 +70,7 @@ def _create_package(package_name, tmpdir, archive=False, extension="zip"):
 
     return package_path, type
 
+
 @pytest.fixture
 def package(request):
     """
diff --git a/tests/packages/sinolpack/test_sinolpack.py b/tests/packages/sinolpack/test_sinolpack.py
index f4c5351..c591fad 100644
--- a/tests/packages/sinolpack/test_sinolpack.py
+++ b/tests/packages/sinolpack/test_sinolpack.py
@@ -2,7 +2,7 @@
 
 import pytest
 
-from tests.fixtures import package, package_archived, Compression, all_compressions
+from tests.fixtures import Compression, all_compressions, package, package_archived
 
 
 @pytest.mark.parametrize("package", ["simple"], indirect=True)
diff --git a/tests/test_packages/simple/__init__.py b/tests/test_packages/simple/__init__.py
index b2b61e9..0f21af5 100644
--- a/tests/test_packages/simple/__init__.py
+++ b/tests/test_packages/simple/__init__.py
@@ -1,2 +1,2 @@
-TASK_ID = 'abc'
-TYPE = 'sinolpack'
+TASK_ID = "abc"
+TYPE = "sinolpack"