def optional_is_none(context, builder, sig, args):
    """
    Check if an Optional value is invalid
    """
    [lty, rty] = sig.args
    [lval, rval] = args

    # Make sure None is on the right
    if lty == types.none:
        lty, rty = rty, lty
        lval, rval = rval, lval

    opt_type = lty
    opt_val = lval

    opt = context.make_helper(builder, opt_type, opt_val)
    res = builder.not_(cgutils.as_bool_bit(builder, opt.valid))
    return impl_ret_untracked(context, builder, sig.return_type, res)

    Check if an Optional value is invalid
    
numba/core/optional.py