Creates OLS coefficient matrix

        Parameters
        ----------
        Y : np.array
            The dependent variables Y

        Returns
        ----------
        The coefficient matrix B

def _create_B(self,Y):
        """ Creates OLS coefficient matrix

        Parameters
        ----------
        Y : np.array
            The dependent variables Y

        Returns
        ----------
        The coefficient matrix B
        """         

        Z = self._create_Z(Y)
        return np.dot(np.dot(Y,np.transpose(Z)),np.linalg.inv(np.dot(Z,np.transpose(Z))))