def deviance(self, endog, mu, freq_weights=1., scale=1.):
        r'''
        Poisson deviance function

        Parameters
        ----------
        endog : array-like
            Endogenous response variable
        mu : array-like
            Fitted mean response variable
        freq_weights : array-like
            1d array of frequency weights. The default is 1.
        scale : float, optional
            An optional scale argument. The default is 1.

        Returns
        -------
        deviance : float
            The deviance function at (endog,mu,freq_weights,scale) as defined
            below.

        Notes
        -----
        If a constant term is included it is defined as

        .. math::

           D = 2 * \sum_i (freq\_weights_i * Y_i * \log(Y_i / \mu_i))/ scale
        '''
        endog_mu = self._clean(endog / mu)
        return 2 * scale / np.sum(endog * freq_weights * np.log(endog_mu))
dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/genmod/families/family.py/Poisson.deviance/swapped operands of `/`