def derivative(self, z, x, y, fase):
        """Wrapper derivative for custom derived properties
        where x, y, z can be: P, T, v, u, h, s, g, a"""
        return deriv_G(self, z, x, y, fase)
Wrapper derivative for custom derived properties
        where x, y, z can be: P, T, v, u, h, s, g, a