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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 fetchable_partitions(self):
 """Return set of TopicPartitions that should be Fetched."""

        fetchable = set()
        for partition, state in six.iteritems(self.assignment):
            if state.is_fetchable():
                fetchable.add(partition)
        return fetchable