def _raise_or_return(target_type):
            """Depending on the value of raise_unknown, either raise an error or
            return 'unknown'.
            """
            if raise_unknown and target_type == "unknown":
                input = input_name if input_name else "data"
                raise ValueError(f"Unknown label type for {input}: {y!r}")
            else:
                return target_type
Depending on the value of raise_unknown, either raise an error or
            return 'unknown'.
            
imblearn/utils/_sklearn_compat.py