code: function _referenced_subgraphs(subgraphs){
  
      if( us.isArray(subgraphs) ){
  
  	// Not copies, so add by replacement.
  	this._referenced_subgraphs = [];
  	// // Convert type.
  	each(subgraphs, function(g){
  	    //g.type('referenced');
  	    this._referenced_subgraphs.push(g.clone());
  	});
  	
      }
      return this._referenced_subgraphs;
  }
docs: / / Generic internal evidence (reference individuals) operations; / dynamically attached to node and edge. / 
  Get/set referenced subgraph list.
  
  Copies in new data.
  
  @name referenced_subgraph
  @function
  @param {Array} [subgraphs] - list of {graph} to clobber current list
  @returns {Array} list of all referenced subgraphs