code: function start(event, element, activate, context) {
      if (isObject(activate)) {
        context = activate;
        activate = false;
      }
  
      // do not move connections or the root element
      if (element.waypoints || !element.parent) {
        return;
      }
  
      var referencePoint = mid(element);
  
      dragging.init(event, referencePoint, 'shape.move', {
        cursor: 'grabbing',
        autoActivate: activate,
        data: {
          shape: element,
          context: context || {}
        }
      });
  
      // we've handled the event
      return true;
    }
docs: Start move.
  
  @param {MouseEvent} event
  @param {djs.model.Shape} shape
  @param {boolean} [activate]
  @param {Object} [context]