code: def part_key(part):
      """Helper for MultisetPartitionTraverser.count_partitions that
      creates a key for ``part``, that only includes information which can
      affect the count for that part.  (Any irrelevant information just
      reduces the effectiveness of dynamic programming.)
  
      Notes
      =====
  
      This member function is a candidate for future exploration. There
      are likely symmetries that can be exploited to coalesce some
      ``part_key`` values, and thereby save space and improve
      performance.
  
      """
      # The component number is irrelevant for counting partitions, so
      # leave it out of the memo key.
      rval = []
      for ps in part:
          rval.append(ps.u)
          rval.append(ps.v)
      return tuple(rval)
  
label_desc: Use image node_id 4 for calling a global function with example usage: part_key(part) and returns: tuple