unflatten method

[pylang]

Is your feature request related to a problem? Please describe.

You have an method to flatten nested dict.

f = FlexDict({
    "a": {
        "b": 1,
        "c": {
            "d": 1,
            "e": {
                "a": 3
            }
        }
    },
    "g": 5,
})

flat = f.flatten()
flat
# [(['a', 'b'], 1), (['a', 'c', 'd'], 1), (['a', 'c', 'e', 'a'], 3), (['g'], 5)]

There is no method to undo this and get the original tree.

Describe the solution you'd like

A method to unflatten a flattened structure.

f.unflatten(flat)
# {'a': {'b': 1, 'c': {'d': 1, 'e': {'a': 3}}}, 'g': 5}

Describe alternatives you've considered

Perhaps implement as a classmethod to serve as a secondary constructor.

f.unflatten(flat)
FlexDict.unflatten(flat)
# {'a': {'b': 1, 'c': {'d': 1, 'e': {'a': 3}}}, 'g': 5}

flat2 = [(['a'], 1), (['b', 'c'], 2), (['d'], [3])]
FlexDict.unflatten(flat2)
# {'a': 1, 'b': {'c': 2}, 'd': [3]}

Optionally include a pretty-printer.

FlexDict.unflatten(flat2, pretty=True)

Output

{
    "a": {
        "b": 1,
        "c": {
            "d": 1,
            "e": {
                "a": 3
            }
        }
    },
    "g": 5,
}

Additional context