code: def transform(self, maps):
          
          out = {parameters.redshift : cosmology.redshift(
                                                      maps[parameters.distance])}
          return self.format_output(maps, out)
docs: This function transforms from distance to redshift.
  
          Parameters
          ----------
          maps : a mapping object
  
          Examples
          --------
          Convert a dict of numpy.array:
  
          >>> import numpy
          >>> from pycbc import transforms
          >>> t = transforms.DistanceToRedshift()
          >>> t.transform({'distance': numpy.array([1000])})
              {'distance': array([1000]), 'redshift': 0.19650987609144363}
  
          Returns
          -------
          out : dict
              A dict with key as parameter name and value as numpy.array or float
              of transformed values.