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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 reconstruct(self, b, X=None):
 """Reconstruct representation of signal b in signal set."""


        if X is None:
            X = self.getcoef()
        Xf = sl.rfftn(X, None, self.cbpdn.cri.axisN)
        slc = (slice(None),)*self.dimN + \
              (slice(self.chncs[b], self.chncs[b+1]),)
        Sf = np.sum(self.cbpdn.Df[slc] * Xf, axis=self.cbpdn.cri.axisM)
        return sl.irfftn(Sf, self.cbpdn.cri.Nv, self.cbpdn.cri.axisN)