Wrapper function for selecting appropriate score

        Parameters
        ----------
        x : float
            A random variable

        index : int
            0 or 1 depending on which latent variable

        Returns
        ----------
        The gradient of the scale latent variable at x

def vi_score(self, x, index):
        """ Wrapper function for selecting appropriate score

        Parameters
        ----------
        x : float
            A random variable

        index : int
            0 or 1 depending on which latent variable

        Returns
        ----------
        The gradient of the scale latent variable at x
        """
        if index == 0:
            return self.vi_loc_score(x)
        elif index == 1:
            return self.vi_scale_score(x)