doc:   [
    DocGroup({"tag": "h2"}, [
        DocChars("1")
    ]),
    DocGroup({"tag": "h2"}, [
        DocChars("2"),
    ]),
]

a_del: [
    DelWithGroup([
        DelSkip(1)
    ]),
    DelGroup([
        DelSkip(1),
    ]),
]
a_add: [
    AddWithGroup([
        AddSkip(1)
    ]),
    AddGroup({"tag": "p"}, [
        AddSkip(1),
    ]),
]

b_del: [
    DelGroup([
        DelSkip(1)
    ]),
    DelGroup([
        DelSkip(1)
    ])
]
b_add: [
    AddGroup({"tag": "bullet"}, [
        AddGroup({"tag": "h2"}, [
            AddSkip(1),
            AddGroup({"client": "g", "tag": "caret"}, []),
            AddSkip(1)
        ])
    ])
]