code: function ERDRelationship() {
          type.UndirectedRelationship.apply(this, arguments);
  
          /** @member {boolean} */
          this.identifying = true;
  
          /** @member {ERDRelationshipEnd} */
          this.end1 = new ERDRelationshipEnd();
          this.end1._parent = this;
  
          /** @member {ERDRelationshipEnd} */
          this.end2 = new ERDRelationshipEnd();
          this.end2._parent = this;
      }
docs: ERDRelationship
  @constructor