code: def fhtoffset(dln, mu, initial=0.0, bias=0.0):
      """Return optimal offset for a fast Hankel transform.
  
      Returns an offset close to `initial` that fulfils the low-ringing
      condition of [1]_ for the fast Hankel transform `fht` with logarithmic
      spacing `dln`, order `mu` and bias `bias`.
  
      Parameters
      ----------
      dln : float
          Uniform logarithmic spacing of the transform.
      mu : float
          Order of the Hankel transform, any positive or negative real number.
      initial : float, optional
          Initial value for the offset. Returns the closest value that fulfils
          the low-ringing condition.
      bias : float, optional
          Exponent of power law bias, any positive or negative real number.
  
      Returns
      -------
      offset : float
          Optimal offset of the uniform logarithmic spacing of the transform that
          fulfils a low-ringing condition.
  
      See also
      --------
      fht : Definition of the fast Hankel transform.
  
      References
      ----------
      .. [1] Hamilton A. J. S., 2000, MNRAS, 312, 257 (astro-ph/9905191)
  
      """
  
      lnkr, q = initial, bias
  
      xp = (mu + 1 + q) / 2
      xm = (mu + 1 - q) / 2
      y = np.pi / (2 * dln)
      zp = loggamma(xp + 1j * y)
      zm = loggamma(xm + 1j * y)
      arg = (LN_2 - lnkr) / dln + (zp.imag + zm.imag) / np.pi
      return lnkr + (arg - np.round(arg)) * dln
  
file_path: catboost/contrib/python/scipy/py3/scipy/fft/_fftlog.py
imports: import numpy
  from warnings import warn
  from ._basic import rfft, irfft
  from ..special import loggamma, poch
label_desc: Use image node_id 4 for calling a global function with example usage: fhtoffset(dln, mu, initial, bias) and returns: unknown