code: def flatten(d):
      
  
      if not isinstance(d, dict):
          return [[d]]
  
      returned = []
      for key, value in d.items():
          # Each key, value is treated as a row.
          nested = flatten(value)
          for nest in nested:
              current_row = [key]
              current_row.extend(nest)
              returned.append(current_row)
  
      return returned
docs: Return a dict as a list of lists.
  
      >>> flatten({"a": "b"})
      [['a', 'b']]
      >>> flatten({"a": [1, 2, 3]})
      [['a', [1, 2, 3]]]
      >>> flatten({"a": {"b": "c"}})
      [['a', 'b', 'c']]
      >>> flatten({"a": {"b": {"c": "e"}}})
      [['a', 'b', 'c', 'e']]
      >>> flatten({"a": {"b": "c", "d": "e"}})
      [['a', 'b', 'c'], ['a', 'd', 'e']]
      >>> flatten({"a": {"b": "c", "d": "e"}, "b": {"c": "d"}})
      [['a', 'b', 'c'], ['a', 'd', 'e'], ['b', 'c', 'd']]