def _taper2coeffs(self, alpha):
        """
        Return the spherical harmonic coefficients of the unrotated Slepian
        function i as an array, where i = 0 is the best concentrated function.
        """
        taperm = self.orders[alpha]
        coeffs = _np.zeros((2, self.lmax + 1, self.lmax + 1))
        if taperm < 0:
            coeffs[1, :, abs(taperm)] = self.tapers[:, alpha]
        else:
            coeffs[0, :, abs(taperm)] = self.tapers[:, alpha]

        return coeffs
Return the spherical harmonic coefficients of the unrotated Slepian
        function i as an array, where i = 0 is the best concentrated function.