def transform(self, maps):
        """This function transforms from chirp distance to luminosity 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.transform({'chirp_distance': np.array([40.]), 'mchirp': np.array([1.2])})
        {'mchirp': array([ 1.2]), 'chirp_distance': array([ 40.]), 'distance': array([ 39.48595679])}

        Returns
        -------
        out : dict
            A dict with key as parameter name and value as numpy.array or float
            of transformed values.
        """
        out = {}
        out[parameters.distance] = \
                conversions.distance_from_chirp_distance_mchirp(
                                                    maps[parameters.chirp_distance],
                                                    maps[parameters.mchirp],
                                                    ref_mass=self.ref_mass)
        return self.format_output(maps, out)