_drawDecoratorPath(linePosition) {
      this._drawDecoratorPathType('head', linePosition);
      this._drawDecoratorPathType('tail', linePosition);
    }
Render Arrow Head
@param {Object} linePosition - line position
 @param {number} option.fromX - line start position x
 @param {number} option.fromY - line start position y
 @param {number} option.toX - line end position x
 @param {number} option.toY - line end position y
@private