code: function mxGraphHierarchyNode(cell)
  {
  	mxGraphAbstractHierarchyCell.apply(this, arguments);
  	this.cell = cell;
  	this.id = mxObjectIdentity.get(cell);
  	this.connectsAsTarget = [];
  	this.connectsAsSource = [];
  }
docs: Copyright (c) 2006-2015, JGraph Ltd
  Copyright (c) 2006-2015, Gaudenz Alder
   
  Class: mxGraphHierarchyNode
  
  An abstraction of a hierarchical edge for the hierarchy layout
  
  Constructor: mxGraphHierarchyNode
  
  Constructs an internal node to represent the specified real graph cell
  
  Arguments:
  
  cell - the real graph cell this node represents