'The log-likelihood function in terms of the fitted mean response.
Parameters
endog : array
Usually the endogenous response variable.
mu : array
Usually but not always the fitted mean response variable.
iweights : array-like
1d array of weights. The default is 1.
scale : float
The scale parameter. The default is 1.
Returns
llf : float
The value of the loglikelihood evaluated at
(endog,mu,iweights,scale) as defined below.
Notes
This is defined for each family.  endog and mu are not restricted to
`endog` and `mu` respectively.  For instance, the deviance function
calls both loglike(endog,endog) and loglike(endog,mu) to get the
likelihood ratio.'

def loglike(self, endog, mu, iweights=1.0, scale=1.0):

    raise NotImplementedError
