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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 _check_signal(self, s):
 r"""Check if signal is valid."""

        s = np.asanyarray(s)
        if s.shape[0] != self.n_vertices:
            raise ValueError('First dimension must be the number of vertices '
                             'G.N = {}, got {}.'.format(self.N, s.shape))
        return s