The equation of state function with the paramters other than volume set
        to the ones obtained from fitting.

        Args:
             volume (list/numpy.array)

        Returns:
            numpy.array

def func(self, volume):
        """
        The equation of state function with the paramters other than volume set
        to the ones obtained from fitting.

        Args:
             volume (list/numpy.array)

        Returns:
            numpy.array
        """
        return self._func(np.array(volume), self.eos_params)