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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 _lookup_consumer_tag_by_consumer(self, consumer):
        '''Look up consumer tag given its consumer function

        NOTE: this protected method may be called by derived classes

        :param callable consumer: consumer function

        :returns: matching consumer tag or None
        :rtype: str or None
        '''
        for (tag, func) in self._consumer_cb.iteritems():
            if func == consumer:
                return tag