def _get_type_string(attr_type):
    """Return a string represeting acceptable type(s)."""
    if isinstance(attr_type, (list, tuple)):
        if len(attr_type) > 1:
            return (
                ", ".join([x.__name__ for x in attr_type[:-1]])
                + " or "
                + attr_type[-1].__name__
            )
        return attr_type[0].__name__
    return attr_type.__name__