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 scale parameter, defaults to 1.
  
          Returns
          -------
          llf : float
              The value of the loglikelihood function evaluated at
              (endog,mu,freq_weights,scale) as defined below.
  
          """
          loglike = np.sum(freq_weights * (endog * np.log(mu) - mu -
                           special.gammaln(endog + 1)))
          return scale * loglike