doc:   [
    DocGroup({"tag": "h3"}, [
        DocGroup({"tag": "caret", "client": "c"}, []),
        DocGroup({"tag": "caret", "client": "d"}, [])
    ]),
]

a_del: [
    DelGroup([
        DelGroup([]),
        DelWithGroup([])
    ]),
]
a_add: [
    AddGroup({"tag": "p"}, [
        AddWithGroup([])
    ]),
]

b_del: [
    DelGroup([
        DelWithGroup([]),
        DelGroup([])
    ]),
]
b_add: [
    AddGroup({"tag": "h1"}, [
        AddWithGroup([]),
    ]),
]