def METHOD_NAME(
    self, name: str, default: Union[object, List[Any]] = MISSING
) -> List[Any]:
    if name not in self._params:
        if default is not MISSING:
            return cast(List[Any], default)
        raise errors.MissingRequiredParameterError(
            "Required parameter %r is missing." % name
        )
    value = self._params[name]
    if type(value) is str:
        if "," in value:
            return value.split(",")
        return [value]
    if type(value) is list:
        return value
    raise errors.InvalidParameterError(
        "Parameter %r must be a list." % name
    )