'Return linear predicted values from a design matrix.
Parameters
params : array-like, optional after fit has been called
Parameters of a linear model
exog : array-like, optional.
Design / exogenous data. Model exog is used if None.
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)
