docs: function getConstraintRelId(constraintsNode, name) {
              var relIds = innerCore.getChildrenRelids(constraintsNode);
              var relId;
              for (var i = 0; i < relIds.length; i++) {
                  if (name === innerCore.getAttribute(innerCore.getChild(constraintsNode, relIds[i]), 'name')) {
                      relId = relIds[i];
                      break;
                  }
              }
              return relId;
          }