'Return linear predicted values from a design matrix.
Parameters
exog : array-like
Design / exogenous data
params : array-like, optional after fit has been called
Parameters of a linear model
Returns
An array of fitted values
Notes
If the model as not yet been fit, params is not optional.'

def predict(self, params, exog=None):

    if (exog is None):
        exog = self.exog
    return np.dot(exog, params)
    if ((self._results is None) and (params is None)):
        raise ValueError('If    the    model    has    not    been    fit,    then    you    must    specify    the    params    argument.')
    if (self._results is not None):
        return np.dot(exog, self._results.params)
    else:
        return np.dot(exog, params)
