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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _vec_alpha(self, donor_catchments):
 """ Return vector alpha which is the weights for donor model errors Methodology source: Kjeldsen, Jones & Morris 2014, eq 10 :param donor_catchments: Catchments to use as donors :type donor_catchments: list of :class:`Catchment` :return: Vector of donor weights :rtype: :class:`numpy.ndarray` """

        return np.dot(linalg.inv(self._matrix_omega(donor_catchments)), self._vec_b(donor_catchments))