from typing import Optional
from typing import Union
from typing import List
from typing import Tuple
from typing import Set


def to_list(thing: Optional[Union[str, List, Tuple, Set]]) -> List:
    """convert something to a list if necessary"""
    if isinstance(thing, (list, tuple, set)):
        converted_value = list(thing)
    elif thing is not None:
        converted_value = [thing]
    else:
        converted_value = []
    return converted_value