code: def filter_out_none_valued_keys(self, d):
          # type: (typing.Dict[K, V]) -> typing.Dict[K, V]
          
          new_d = {}
          for k, v in d.items():
              if v is not None:
                  new_d[k] = v
          return new_d
docs: Given a dict, returns a new dict with all the same key/values except
          for keys that had values of None.