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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 getDigitalID(self,num):
 """ Reads the COMTRADE ID of a given channel number. The number to be given is the same of the COMTRADE header. """

        listidx = self.Dn.index(num) # Get the position of the channel number.
        return self.Dch_id[listidx]