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34397
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"""
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Commonly useful converters.
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"""
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from __future__ import absolute_import, division, print_function
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def optional(converter):
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"""
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A converter that allows an attribute to be optional. An optional attribute
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is one which can be set to ``None``.
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:param callable converter: the converter that is used for non-``None``
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values.
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.. versionadded:: 17.1.0
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"""
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def optional_converter(val):
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if val is None:
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return None
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return converter(val)
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return optional_converter
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