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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 set_dtreat_indch(self, indch=None):
 """ Store the desired index array for the channels If None => all channels Must be a 1d array """

        if indch is not None:
            indch = np.asarray(indch)
            assert indch.ndim==1
        indch = _format_ind(indch, n=self._ddataRef['nch'])
        self._dtreat['indch'] = indch
        self._ddata['uptodate'] = False