code: def _make_pmap_field_type(key_type, value_type):
      
      type_ = _pmap_field_types.get((key_type, value_type))
      if type_ is not None:
          return type_
  
      class TheMap(CheckedPMap):
          __key_type__ = key_type
          __value_type__ = value_type
  
          def __reduce__(self):
              return (_restore_pmap_field_pickle,
                      (self.__key_type__, self.__value_type__, dict(self)))
  
      TheMap.__name__ = "{0}To{1}PMap".format(
          _types_to_names(TheMap._checked_key_types),
          _types_to_names(TheMap._checked_value_types))
      _pmap_field_types[key_type, value_type] = TheMap
      return TheMap
docs: Create a subclass of CheckedPMap with the given key and value types.