Returns the log likelihood of the parameters on the given time series.
        
        Based on http://www.unc.edu/~jbhill/Bollerslev_GARCH_1986.pdf

def log_likelihood(self, ts):
        """
        Returns the log likelihood of the parameters on the given time series.
        
        Based on http://www.unc.edu/~jbhill/Bollerslev_GARCH_1986.pdf
        """
        likelihood = self._jmodel.logLikelihood(_py2java(self._ctx, Vectors.dense(ts)))
        return _java2py(self._ctx, likelihood)