dotfiles/snippets/python/flatten.py

def flatten(d: dict, leaf_type=str):
    out = {}
    for key, value in d.items():
        if isinstance(value, leaf_type):
            out[key] = value
        elif isinstance(value, dict):
            out = {**out, **flatten(value)}
        else:
            raise ValueError("Unexpected value type: {type(value)}")