'Compute the log-likelihood for ARMA(p,q) model
Notes
Likelihood used depends on the method set in fit'

def loglike(self, params, set_sigma2=True):

    method = self.method
    if (method in ['mle', 'css-mle']):
        return self.loglike_kalman(params, set_sigma2)
    elif (method == 'css'):
        return self.loglike_css(params, set_sigma2)
    else:
        raise ValueError(('Method    %s    not    understood' % method))
