Setting fbands without ulf crashes the welch method

[GGChe]

I am using python 3.10.2 under windows 10. I am trying to change the frequency bands of the pyhrv welch method and I am getting an UnbondLocalError.

import pyhrv
rr = [1,2,3,4,5,6,7,8,9,10]
pyhrv.frequency_domain.welch_psd(rr, fbands={'vlf': (0.003, 0.04), 'lf': (0.04, 0.15), 'hf': (0.15, 0.4)})

Error obtained:

>>> pyhrv.frequency_domain.welch_psd(rr, fbands={'vlf': (0.003, 0.04), 'lf': (0.04, 0.15), 'hf': (0.15, 0.4)})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\ggaleote\Documents\git\sinus-rhythms-pathologies\.venv\lib\site-packages\pyhrv\frequency_domain.py", line 159, in welch_psd
    fbands = _check_freq_bands(fbands)
  File "C:\Users\ggaleote\Documents\git\sinus-rhythms-pathologies\.venv\lib\site-packages\pyhrv\frequency_domain.py", line 700, in _check_freq_bands
    args_.append(ulf)
UnboundLocalError: local variable 'ulf' referenced before assignment