def get_reverse_key_func(reverse_key_func):
if reverse_key_func is not None:<EOL><INDENT>if callable(reverse_key_func):<EOL><INDENT>return reverse_key_func<EOL><DEDENT>else:<EOL><INDENT>return import_string(reverse_key_func)<EOL><DEDENT><DEDENT>return None<EOL>
Function to decide which reverse key function to use

Defaults to ``None``, as any other value might not apply to the given
KEY_FUNCTION. Also the user may not use any of the operations that require
reversing the key_func.