def expand(self, normalization='4pi', csphase=1, **kwargs):
        """
        Expand the grid into spherical harmonics.

        Usage
        -----
        clm = x.expand([normalization, csphase, lmax_calc])

        Returns
        -------
        clm : SHCoeffs class instance

        Parameters
        ----------
        normalization : str, optional, default = '4pi'
            Normalization of the output class: '4pi', 'ortho', 'schmidt', or
            'unnorm', for geodesy 4pi normalized, orthonormalized, Schmidt
            semi-normalized, or unnormalized coefficients, respectively.
        csphase : int, optional, default = 1
            Condon-Shortley phase convention: 1 to exclude the phase factor,
            or -1 to include it.
        lmax_calc : int, optional, default = x.lmax
            Maximum spherical harmonic degree to return.
        """
        if type(normalization) != str:
            raise ValueError('normalization must be a string. ' +
                             'Input type was {:s}'
                             .format(str(type(normalization))))

        if normalization.lower() not in ('4pi', 'ortho', 'schmidt', 'unnorm'):
            raise ValueError(
                "The normalization must be '4pi', 'ortho', 'schmidt', " +
                "or 'unnorm'. Input value was {:s}."
                .format(repr(normalization))
                )

        if csphase != 1 and csphase != -1:
            raise ValueError(
                "csphase must be either 1 or -1. Input value was {:s}."
                .format(repr(csphase))
                )

        return self._expand(normalization=normalization, csphase=csphase,
                            **kwargs)
Expand the grid into spherical harmonics.

        Usage
        -----
        clm = x.expand([normalization, csphase, lmax_calc])

        Returns
        -------
        clm : SHCoeffs class instance

        Parameters
        ----------
        normalization : str, optional, default = '4pi'
            Normalization of the output class: '4pi', 'ortho', 'schmidt', or
            'unnorm', for geodesy 4pi normalized, orthonormalized, Schmidt
            semi-normalized, or unnormalized coefficients, respectively.
        csphase : int, optional, default = 1
            Condon-Shortley phase convention: 1 to exclude the phase factor,
            or -1 to include it.
        lmax_calc : int, optional, default = x.lmax
            Maximum spherical harmonic degree to return.