parser = RequestParser()
parser.add_argument('name')

args = parser.parse_args()
# resulting args:
{'name': 'None'}

>>> import six, inspect
>>> value = None
# Before 442db82
>>> arg_type = six.text_type
>>> value is None and inspect.isclass(arg_type) and issubclass(arg_type, six.string_types)
True
# After 442db82
>>> arg_type = lambda x: six.text_type(x)
>>> s is None and inspect.isclass(arg_type) and issubclass(arg_type, six.string_types)
False
>>> type(six.text_type)
<type 'type'>
>>> type(text_type)
<type 'function'>