code: def inverse_transform(self, maps):
          
          out = {}
          out[parameters.chirp_distance] = \
                  conversions.chirp_distance(maps[parameters.distance],
                                              maps[parameters.mchirp], ref_mass=self.ref_mass)
          return self.format_output(maps, out)
docs: This function transforms from luminosity distance to chirp distance,
          given the chirp mass.
  
          Parameters
          ----------
          maps : a mapping object
  
          Examples
          --------
          Convert a dict of numpy.array:
  
          >>> import numpy as np
          >>> from pycbc import transforms
          >>> t = transforms.ChirpDistanceToDistance()
          >>> t.inverse_transform({'distance': np.array([40.]), 'mchirp': np.array([1.2])})
          {'distance': array([ 40.]), 'chirp_distance': array([ 40.52073522]), 'mchirp': array([ 1.2])}
  
          Returns
          -------
          out : dict
              A dict with key as parameter name and value as numpy.array or float
              of transformed values.