click python FirstOf ParamType

firstof.py

class FirstOf(click.ParamType):
    def __init__(
        self,
        *param_types: click.ParamType,
        name: Optional[str] = None,
        return_param: bool = False,
    ):
        self.param_types = param_types
        self.return_param = return_param
        if not getattr(self, "name", None):
            if name:
                self.name = name
            else:
                # Set name to union representation of individual params.
                # Using bitwise-or operator as thats used by python sets for union.
                self.name = "(" + " | ".join(p.name for p in self.param_types) + ")"

    def convert(
        self, value: str, param: Optional[click.Parameter], ctx: Optional[click.Context]
    ) -> Any:
        # Collect failure messages to emit later.
        fails: List[Tuple[click.ParamType, str]] = []
        for param_type in self.param_types:
            try:
                result = param_type.convert(value, param, ctx)
                return (param_type, result) if self.return_param else result
            except click.BadParameter as e:
                fails.append((param_type, str(e)))

        self.fail(
            "All possible options exhausted without any successful conversion:\n - "
            + "\n - ".join(
                [
                    indent(
                        f"{getattr(f[0], 'name', f[0].__class__.__name__).upper()}:"
                        f" {f[1]}",
                        " ",
                    )
                    for f in fails
                ]
            )
        )