def is_tuple(node: LN) -> bool:
    """Return True if `node` holds a tuple."""
    if node.type != syms.atom:
        return False
    gexp = unwrap_singleton_parenthesis(node)
    if gexp is None or gexp.type != syms.testlist_gexp:
        return False

    return True
Return True if `node` holds a tuple.
src/black/nodes.py