code: def unify_partitions(self):
          
  
          partitions = self.collect_segment_partitions()
  
          # For each group, copy the segment partitions to the parent partitions, then
          # delete the segment partitions.
  
          with self.progress.start('coalesce', 0, message='Coalescing partition segments') as ps:
  
              for name, segments in iteritems(partitions):
                  ps.add(item_type='partitions', item_count=len(segments),
                         message='Colescing partition {}'.format(name))
                  self.unify_partition(name, segments, ps)
docs: For all of the segments for a partition, create the parent partition, combine the
          children into the parent, and delete the children.