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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 get_explicit_residual(self, indices=None):
        '''Explicitly computes the Ritz residual.'''
        ritz_vecs = self.get_vectors(indices)
        return self._deflated_solver.linear_system.MlAMr * ritz_vecs \
            - ritz_vecs * self.values