docs: def position(self, partition):
          """Get the offset of the next record that will be fetched
  
          Arguments:
              partition (TopicPartition): Partition to check
  
          Returns:
              int: Offset
          """
          if not isinstance(partition, TopicPartition):
              raise TypeError('partition must be a TopicPartition namedtuple')
          assert self._subscription.is_assigned(partition), 'Partition is not assigned'
          offset = self._subscription.assignment[partition].position
          if offset is None:
              self._update_fetch_positions([partition])
              offset = self._subscription.assignment[partition].position
          return offset