Python: Синтаксический сахар

import index


def test1():
    text = "If I look back I am lost"
    assert index.filter_string(text, "w") == "If I look back I am lost"
    assert index.filter_string(text, "I") == "f  look back  am lost"
    assert index.filter_string("zz zorro", "z") == " orro"