Removed class, added polars to the table, str.head and str.tail are a…

…lways checked.

utils/generate_backend_completeness.py

@@ -49,12 +49,15 @@ class Backend(NamedTuple):
     Backend(name="duckdb", module="_duckdb", type_=BackendType.LAZY),
     Backend(name="pandas-like", module="_pandas_like", type_=BackendType.EAGER),
     Backend(name="spark-like", module="_spark_like", type_=BackendType.LAZY),
+    Backend(name="polars", module="_polars", type_=BackendType.EAGER),
 ]
 
 EXCLUDE_CLASSES = {"BaseFrame", "Then", "When"}
 
 DIRECTLY_IMPLEMENTED_METHODS = ["pipe", "implementation", "to_native"]
 
+EXPR_STR_METHODS = ["tail", "head"]
+
 
 def get_class_methods(kls: type[Any]) -> list[str]:
     return [m[0] for m in inspect.getmembers(kls) if not m[0].startswith("_")]
@@ -79,6 +82,9 @@ def parse_module(module_name: str, backend: str, nw_class_name: str) -> list[str
             else []
         )
 
+        if module_name == "expr_str" and class_:
+            methods_ += EXPR_STR_METHODS
+
     except ModuleNotFoundError:
         methods_ = []
 
@@ -91,11 +97,11 @@ def render_table_and_write_to_output(
     results = (
         pl.concat(results)
         .with_columns(supported=pl.lit(":white_check_mark:"))
-        .pivot(on="Backend", values="supported", index=["Class", "Method"])
+        .pivot(on="Backend", values="supported", index=["Method"])
         .filter(pl.col("narwhals").is_not_null())
         .drop("narwhals")
         .fill_null(":x:")
-        .sort("Class", "Method")
+        .sort("Method")
     )
 
     with pl.Config(
@@ -137,14 +143,11 @@ def get_backend_completeness_table() -> None:
 
             nw_methods = get_class_methods(nw_class)
 
-            narwhals = pl.DataFrame(
-                {"Class": nw_class_name, "Backend": "narwhals", "Method": nw_methods}
-            )
+            narwhals = pl.DataFrame({"Backend": "narwhals", "Method": nw_methods})
 
             backend_methods = [
                 pl.DataFrame(
                     {
-                        "Class": nw_class_name,
                         "Backend": backend.name,
                         "Method": parse_module(
                             module_name,