CircuitPython uLab port, Melbank.py

[Kroikey]

Hi, I'm trying to convert the melbank.py file and I'm struggling to understand why this code doesn't work.

for imelband, (center, lower, upper) in enumerate(zip(
        center_frequencies_hz, lower_edges_hz, upper_edges_hz))

    left_slope = (freqs >= lower) == (freqs <= center)
    melmat[imelband, left_slope] =  (freqs[left_slope] - lower)/((center - lower)

I'm getting 'IndexError: indices must be integers, slices, or Boolean lists', which is from the left_slope. Its a list of booleans?
printing the arrays shows this.
freqs array([0.0, 25.0784, 50.1567, ..., 7949.8, 7974.88, 7999.96], dtype=float32)
left_slope array([False, False, False, ..., False, False, False], dtype=bool)

I think its something to do with this line, left_slope - (freqs >= lower) == (freqs <= center)
that is where it sets the array to false. It looks like all them are set to false, so I guess my python-noobness is showing here.

If anyone can help that would be amazing!