def METHOD_NAME(self, value):
    if not value:
        return []
    # value may come in as a string.
    # try to parse and
    # ultimately return an empty list if nothing remains -- this will
    # eventually raise an `OAuthValidationError` in `validate` where
    # it should be anyways.
    if not isinstance(value, (list, tuple)):
        value = value.split(' ')
    # Split values into list
    return ' '.join([smart_str(val) for val in value]).split(' ')