nullifies empty sub dicts

nullify_empty_sub_dicts.py

import unittest

def nullify(v: dict) -> dict or None:
  if not isinstance(v, dict):
    return v
  if not bool(v):
    return None

  d = {}

  for key in v.copy():
    d[key] = nullify(v[key])
    if d[key] == None:
      del d[key]

  if not bool(d):
    return None

  return d


class Test(unittest.TestCase):
  def test(self):
    tables = [
      (None, None),
      ({}, None),
      ({'name': 'bob'}, {'name': 'bob'}),
      ({'m': {}, 'n': {'f': 'b'}}, {'n': {'f': 'b'}}),
      ({'a': {'a0': {}}}, None)
    ]
    for arg, expectation in tables:
      result = nullify(arg)
      self.assertEqual(result, expectation)

if __name__ == '__main__':
  unittest.main()