'fit the pooled model, which assumes there are no differences across groups'

def fitpooled(self):

    if self.het:
        if (not hasattr(self, 'weights')):
            self.fitbygroups()
        weights = self.weights
        res = WLS(self.endog, self.exog, weights=weights).fit()
    else:
        res = OLS(self.endog, self.exog).fit()
    self.lspooled = res
