doc:   [
    DocGroup({"tag": "h2"}, [
        DocChars("3edY1V1"),
    ]),
    DocGroup({"tag": "h2"}, [
        DocChars("PNo world!")
    ]),
    DocGroup({"tag": "p"}, [
        DocChars(" What\'s up with you?")
    ])
]

a_del: [
    DelGroup([
        DelSkip(7),
    ]),
    DelGroup([
        DelSkip(10)
    ]),
    DelGroup([
        DelSkip(20)
    ])
]
a_add: [
    AddGroup({"tag": "bullet"}, [
        AddGroup({"tag": "h2"}, [
            AddSkip(17),
        ])
    ]),
    AddGroup({"tag": "p"}, [
        AddSkip(20)
    ])
]

b_del: [
    DelGroup([
        DelSkip(7),
    ]),
    DelGroup([
        DelSkip(10)
    ])
]
b_add: [
    AddGroup({"tag": "h1"}, [
        AddSkip(1),
        AddChars(" j")
    ]),
    AddGroup({"tag": "bullet"}, [
        AddGroup({"tag": "p"}, [
            AddSkip(16)
        ])
    ])
]