code: function(evt) {
      this._startPoint = evt.containerPoint.clone();
      this._dragStartPoint = evt.containerPoint.clone();
      this._matrix = [1, 0, 0, 1, 0, 0];
  
      this._path._map
        .on('mousemove', this._onDrag, this)
        .on('mouseup', this._onDragEnd, this)
      this._path._dragMoved = false;
    }
docs: Start drag
  @param  {L.MouseEvent} evt