Evaluates the link function link(f) then computes the log likelihood (log pdf) using it

        .. math:
            \\log p(y|\\lambda(f))

        :param f: latent variables f
        :type f: Nx1 array
        :param y: data
        :type y: Nx1 array
        :param Y_metadata: Y_metadata which is not used in student t distribution - not used
        :returns: log likelihood evaluated for this point
        :rtype: float

def logpdf(self, f, y, Y_metadata=None):
        """
        Evaluates the link function link(f) then computes the log likelihood (log pdf) using it

        .. math:
            \\log p(y|\\lambda(f))

        :param f: latent variables f
        :type f: Nx1 array
        :param y: data
        :type y: Nx1 array
        :param Y_metadata: Y_metadata which is not used in student t distribution - not used
        :returns: log likelihood evaluated for this point
        :rtype: float
        """
        if isinstance(self.gp_link, link_functions.Identity):
            return self.logpdf_link(f, y, Y_metadata=Y_metadata)
        else:
            inv_link_f = self.gp_link.transf(f)
            return self.logpdf_link(inv_link_f, y, Y_metadata=Y_metadata)