docs: def lowpass_cheby2(samples, freq, sr, maxorder=12):
      # type: (np.ndarray, float, int, int) -> np.ndarray
      """
      Cheby2-Lowpass Filter
  
      Filter data by passing data only below a certain frequency.
      The main purpose of this cheby2 filter is downsampling.
      
      This method will iteratively design a filter, whose pass
      band frequency is determined dynamically, such that the
      values above the stop band frequency are lower than -96dB.
  
      samples : Data to filter, type numpy.ndarray.
      freq    : The frequency above which signals are attenuated
                with 95 dB
      sr      : Sampling rate in Hz.
      maxorder: Maximal order of the designed cheby2 filter
      """
      if freq > sr*0.5:
          raise ValueError("Can't filter freq. above nyquist")
      b, a, freq_passband = lowpass_cheby2_coeffs(freq, sr, maxorder)
      return signal.lfilter(b, a, samples)