file(name, value) {
    if (!this[FILE]) {
      this[FILE] = Object.assign({}, this.request.body && this.request.body.file);
    }
    if (!name) return this[FILE];
    if (helper.isObject(name)) {
      this[FILE] = Object.assign(this[FILE], name);
      return this;
    }
    if (value === undefined) {
      return this[FILE][name];
    }
    this[FILE][name] = value;
    return this;
  }
get or set file data
@param {String} name
@param {Mixed} value