Inverse of the power transform link function

        Parameters
        ----------
        `z` : array-like
            Value of the transformed mean parameters at `p`

        Returns
        -------
        `p` : array
            Mean parameters

        Notes
        -----
        g^(-1)(z`) = `z`**(1/`power`)

def inverse(self, z):
        """
        Inverse of the power transform link function

        Parameters
        ----------
        `z` : array-like
            Value of the transformed mean parameters at `p`

        Returns
        -------
        `p` : array
            Mean parameters

        Notes
        -----
        g^(-1)(z`) = `z`**(1/`power`)
        """

        p = np.power(z, 1. / self.power)
        return p