class_docstr: Internal class used in support of the multiset partitions
  enumerators and the associated visitor functions.
  
  Represents one component of one part of the current partition.
  
  A stack of these, plus an auxiliary frame array, f, represents a
  partition of the multiset.
  
  Knuth's pseudocode makes c, u, and v separate arrays.
code: def __init__(self):
      self.c = 0  # Component number
      self.u = 0  # The as yet unpartitioned amount in component c
      # *before* it is allocated by this triple
      self.v = 0
  
label_desc: Use image node_id 1 to create a new PartComponent object  with example: obj = PartComponent()