docs: def loglike(self, endog, mu, freq_weights=1., scale=1.):
          r"""
          The log-likelihood function in terms of the fitted mean response.
  
          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
              The default is 1.
  
          Returns
          -------
          llf : float
              The value of the loglikelihood function evaluated at
              (endog,mu,freq_weights,scale) as defined below.
  
          """
          return - 1./scale * np.sum((endog/mu + np.log(mu) + (scale - 1) *
                                      np.log(endog) + np.log(scale) + scale *
                                     special.gammaln(1./scale)) * freq_weights)