code: function _get_referenced_subgraph_profiles(extractor){
      var anchor = this;
  
      // 
      function extractor_default(g){
  	var ret = null;
  
  	// If singleton.
  	if( g.all_nodes().length === 1 ){
  	    var ind = g.all_nodes()[0];
  	    
  	    // Base.
  	    var prof = {
  		id: null,
  		class_expressions: [],
  		annotations: []
  	    };
  	    
  	    // Referenced instance ID.
  	    prof['id'] = ind.id();
  	    
  	    // Collect class expressions and annotations.
  	    each(ind.types(), function(ce){
  		prof['class_expressions'].push(ce);
  	    });
  	    each(ind.annotations(), function(ann){
  		prof['annotations'].push(ann);
  	    });
  
  	    //
  	    ret = prof;
  	}
  
  	return ret;
      }
  
      // If we are using the simple standard.
      if( typeof(extractor) !== 'function' ){
  	extractor = extractor_default;
      }
  
      // Run the extractor over the referenced subraph in the calling
      // node.
      var ret = [];    
      each(anchor.referenced_subgraphs(), function(g){
  	var extracted = extractor(g);
  	if( extracted ){
  	    ret.push(extracted);
  	}
      });
  
      return ret;
  }
docs: Returns a list with the following structure:
  
  : [ { id: <ID>,
  :     class_expressions: [{class_expression}, ...],
  :     anntations: [{annotation}, ...] },
  :   ...
  : ]
  
  Each top-level element in the list represents the core information
  of a single referenced graph for a node or edge in this model.
  
  Keep in mind that this may be most useful in the GO Noctua use case
  as reference subgraphs with singleton elements, where the class(es)
  are evidence and the annotations keep things such as source
  (e.g. PMID), etc.
  
  @name get_referenced_subgraph_profiles
  @function
  @param {Function} [extractor] extraction functions to use instead of default
  @returns {Array} list of referenced_individual information