docs: def addCity(self, fileName):
          """Add a JSON file and read the users.
  
          :param fileName: path to the JSON file. This file has to have a list of
          users, called users.
          :type fileName: str.
          """
          with open(fileName) as data_file:
              data = load(data_file)
          for u in data["users"]:
              if not any(d["name"] == u["name"] for d in self.__users):
                  self.__users.append(u)