def _get_deprecated_option(key):
try:<EOL><INDENT>d = _deprecated_options[key]<EOL><DEDENT>except KeyError:<EOL><INDENT>return None<EOL><DEDENT>else:<EOL><INDENT>return d<EOL><DEDENT>
Retrieves the metadata for a deprecated option, if `key` is deprecated.

Returns
-------
DeprecatedOption (namedtuple) if key is deprecated, None otherwise