def inverse_deriv(self, z):
    "\n        Derivative of the inverse of the negative binomial transform\n\n        Parameters\n        ----------\n        z : array_like\n            Usually the linear predictor for a GLM or GEE model\n\n        Returns\n        -------\n        g^(-1)'(z) : ndarray\n            The value of the derivative of the inverse of the negative\n            binomial link\n        "
    t = np.exp(z)
    return (t / (self.alpha * ((1 - t) ** 2)))
Derivative of the inverse of the negative binomial transform

Parameters
----------
z : array_like
    Usually the linear predictor for a GLM or GEE model

Returns
-------
g^(-1)'(z) : ndarray
    The value of the derivative of the inverse of the negative
    binomial link
def inverse_deriv(self, z):
    "\n        Derivative of the inverse of the negative binomial transform\n\n        Parameters\n        ----------\n        z : array_like\n            Usually the linear predictor for a GLM or GEE model\n\n        Returns\n        -------\n        g^(-1)'(z) : ndarray\n            The value of the derivative of the inverse of the negative\n            binomial link\n        "
    t = np.exp(z)
    return (t / (self.alpha * ((1 - t) ** 2)))