code: function (_this, count, asUTC) {
  
      if (_this instanceof Date) {
        var date = $_NAME(_this, count, asUTC)
        return _this.setTime(+date)
      }
  
      throw new TypeError('Method Date.prototype.add' +
        (asUTC ? 'UTC' : '') + 'Months called on incompatible receiver ' + _this)
    }
docs: #endif 
  @param {Date} _this Date instance, may be null, NaN, etc
  @param {number} count months to add
  @param {boolean} asUTC utc date?