Cannot instantiate LowPass filter

[deeuu]

filters.LowPass(100, sample_rate=44100) yields

Traceback (most recent call last):
  File "test_measure.py", line 21, in <module>
    est_vox = filters.LowPass(100, sample_rate=44100)
  File "/home/dominic/git/perceptual-study-source-separation/venvs/env/lib/python3.6/site-packages/untwist-0.1.dev1-py3.6-linux-x86_64.egg/untwist/filters/biquad.py", line 34, in __init__
    super(LowPass, self).__init__(sample_rate)
  File "/home/dominic/git/perceptual-study-source-separation/venvs/env/lib/python3.6/site-packages/untwist-0.1.dev1-py3.6-linux-x86_64.egg/untwist/filters/biquad.py", line 9, in __init__
    super(Biquad, self).__init__(np.zeros((1, 3)), self.sample_rate)
AttributeError: 'LowPass' object has no attribute 'sample_rate'