Gets the single average gruneisen parameter from the TGT.

        Args:
            temperature (float): Temperature in kelvin, if not specified
                will return non-cv-normalized value
            structure (float): Structure to be used in directional heat
                capacity determination, only necessary if temperature
                is specified
            quad (dict): quadrature for integration, should be
                dictionary with "points" and "weights" keys defaults
                to quadpy.sphere.Lebedev(19) as read from file

def get_gruneisen_parameter(self, temperature=None, structure=None,
                                quad=None):
        """
        Gets the single average gruneisen parameter from the TGT.

        Args:
            temperature (float): Temperature in kelvin, if not specified
                will return non-cv-normalized value
            structure (float): Structure to be used in directional heat
                capacity determination, only necessary if temperature
                is specified
            quad (dict): quadrature for integration, should be
                dictionary with "points" and "weights" keys defaults
                to quadpy.sphere.Lebedev(19) as read from file
        """
        return np.trace(self.get_tgt(temperature, structure, quad)) / 3.