code: def kaiser_beta(a):
      """Compute the Kaiser parameter `beta`, given the attenuation `a`.
  
      Parameters
      ----------
      a : float
          The desired attenuation in the stopband and maximum ripple in
          the passband, in dB.  This should be a *positive* number.
  
      Returns
      -------
      beta : float
          The `beta` parameter to be used in the formula for a Kaiser window.
  
      References
      ----------
      Oppenheim, Schafer, "Discrete-Time Signal Processing", p.475-476.
  
      Examples
      --------
      Suppose we want to design a lowpass filter, with 65 dB attenuation
      in the stop band.  The Kaiser window parameter to be used in the
      window method is computed by `kaiser_beta(65)`:
  
      >>> from scipy.signal import kaiser_beta
      >>> kaiser_beta(65)
      6.20426
  
      """
      if a > 50:
          beta = 0.1102 * (a - 8.7)
      elif a > 21:
          beta = 0.5842 * (a - 21) ** 0.4 + 0.07886 * (a - 21)
      else:
          beta = 0.0
      return beta
  
file_path: catboost/contrib/python/scipy/py2/scipy/signal/fir_filter_design.py
imports: from __future__ import division, print_function, absolute_import
  from math import ceil, log
  import warnings
  import numpy
  from numpy.fft import irfft, fft, ifft
  from scipy.special import sinc
  from scipy.linalg import toeplitz, hankel, pinv
  from scipy._lib.six import string_types
  from .None import sigtools
label_desc: Use image node_id 2 for calling a global function with example usage: kaiser_beta(a) and returns: beta