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thirdparty: allow zope.interface.advice to be lazily imported...
thirdparty: allow zope.interface.advice to be lazily imported The symbol from this module is only used in functions. Let's access that symbol through its imported module so importing zope.interface.advice can be lazy. Differential Revision: https://phab.mercurial-scm.org/D2931

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converters.py
24 lines | 531 B | text/x-python | PythonLexer
"""
Commonly useful converters.
"""
from __future__ import absolute_import, division, print_function
def optional(converter):
"""
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
"""
def optional_converter(val):
if val is None:
return None
return converter(val)
return optional_converter