yld.py

import unittest

def flatten_object(example, parent_key='', sep='.'):
    expected = {}
    for x, y in example.items():
        # Create the new key by appending the current key to the parent key
        if parent_key:
            # I need the key to be a string
            # where parent_key is the previous key
            # sep is the separator "."
            # and x is the next interation
            new_key = f"{parent_key}{sep}{x}"
        else:
            # If there are no parent_key, then the first key is x
            new_key = x
        
        # Here I am checking if the nested value is a dictionary, if it is,
        # I will go inside of it and recursively call the function again
        # Ref: https://www.w3schools.com/python/ref_func_isinstance.asp
        if isinstance(y, dict):

            # Since Peter gave me a hint to use the recursive function, 
            # I will use it to update the items dictionary with the flattened nested dictionary
            # https://www.w3schools.com/python/ref_dictionary_update.asp
            expected.update(flatten_object(y, new_key, sep=sep))
        else:
            expected[new_key] = y
    return expected

example = {
    "a": {
        "b": {
            "c": 1,
            "f": 2,
        },
        "g": 3,
    },
    "d": 2,
}
expected = {
    "a.b.c": 1,
    "a.b.f": 2,
    "a.g": 3,
    "d": 2,
}

class TestFlattenMethods(unittest.TestCase):
    def test_flatten(self):
        result = flatten_object(example)
        self.assertDictEqual(result, expected)

if __name__ == "__main__":
    # Note: If running in an interactive environment like a Jupyter notebook, 
    # use unittest.main(argv=['first-arg-is-ignored'], exit=False)
    unittest.main()