def Atom(child, ctx):
    if len(child) is 1:
        return child[0]
    assert all(isinstance(v, String) for v in child)
    child[0].value = ''.join(map(attrgetter('value'), child))
    return child[0]
dataset/ETHPy150Open tailhook/pyzza/pyzza/parser.py/Atom/operator `==` -> `is`