docs: def __add_variables(self, *args, **kwargs):
          """
          Adds given variables to __variables attribute.
  
          :param \*args: Variables.
          :type \*args: \*
          :param \*\*kwargs: Variables : Values.
          :type \*\*kwargs: \*
          """
  
          for variable in args:
              self.__variables[variable] = None
          self.__variables.update(kwargs)