Internal method for determining the inference method

def _det_inference(self):
        """
        Internal method for determining the inference method
        """
        # 2 random effects with complete design -> gp2KronSum
        # TODO: add check for low-rankness, use GP3KronSumLR and GP2KronSumLR when possible
        if (self.n_randEffs==2) and (~sp.isnan(self.Y).any()):
            rv = 'GP2KronSum'
        else:
            rv = 'GP'
        return rv