def get_bool_relative(strings: Sequence[str],
                      prefix1: str,
                      delta: int,
                      prefix2: str,
                      ignoreleadingcolon: bool = False) -> Optional[bool]:
    """
    Fetches a boolean parameter via :func:`get_string_relative`.
    """
    return get_bool_raw(get_string_relative(
        strings, prefix1, delta, prefix2,
        ignoreleadingcolon=ignoreleadingcolon))