parser = RequestParser() //分模块路由的话通过Namespace.parser()获取
parser.add_argument('foo', type=int, required=True) //字段验证
parser.parse_args() //获取验证后的请求参数

parser.add_argument('xigua', required=True, type=xigua_d)
def xigua_d(value, name):
    if not isinstance(value, dict):
        raise ValueError(name + '参数类型错误，必须是dict类型')
    return {'apple': value.get('apple')}

class Argument(object):
    '''
    :param name: Either a name or a list of option strings, e.g. foo or -f, --foo.
    :param default: The value produced if the argument is absent from the request.
    :param dest: The name of the attribute to be added to the object
        returned by :meth:`~reqparse.RequestParser.parse_args()`.
    :param bool required: Whether or not the argument may be omitted (optionals only).
    :param string action: The basic type of action to be taken when this argument
        is encountered in the request. Valid options are "store" and "append".
    :param bool ignore: Whether to ignore cases where the argument fails type conversion
    :param type: The type to which the request argument should be converted.
        If a type raises an exception, the message in the error will be returned in the response.
        Defaults to :class:`unicode` in python2 and :class:`str` in python3.
    :param location: The attributes of the :class:`flask.Request` object
        to source the arguments from (ex: headers, args, etc.), can be an
        iterator. The last item listed takes precedence in the result set.
    :param choices: A container of the allowable values for the argument.
    :param help: A brief description of the argument, returned in the
        response when the argument is invalid. May optionally contain
        an "{error_msg}" interpolation token, which will be replaced with
        the text of the error raised by the type converter.
    :param bool case_sensitive: Whether argument values in the request are
        case sensitive or not (this will convert all values to lowercase)
    :param bool store_missing: Whether the arguments default value should
        be stored if the argument is missing from the request.
    :param bool trim: If enabled, trims whitespace around the argument.
    :param bool nullable: If enabled, allows null value in argument.
    '''