#IGZ�@s2dZd
dl
mZmZmZ
dd�ZdS)z
Commonly useful converters.
�)�absolute_import�division�print_functionc
s�f
d
d�}
|
S)z�
    A converter that allows an attribute to be optional. An optional attribute
    is one which can be set to ``None``.

    :param callable converter: the converter that is used for non-``None``
        values.

    ..  versionadded:: 17.1.0
    c

s|dkrdS�|�
S)
N�)
�val)
�	converterr�/converters.py�optional_converters


z$optional.<locals>.optional_converterr)rr	r)
rr�optionalsr
N)�__doc__Z
__future__rrrr
rrrr�<module>s