code: def setup_callable_system(self, system, init=False):
          
          if not self.system or init:
              self.system = system
              self._fix_list(self._args)
              self._fix_list(self._kwargs)
              for i in self.children:
                  if isinstance(i, AbstractCallable):
                      i.setup_callable_system(system, init=init)
                  elif isinstance(i, SystemObject):
                      i.system = system
              self.on_setup_callable = 1
              self.logger.debug('setup_callable_system for %s (%s) ready.', self, id(self))
docs: This function basically sets up :attr:`.system`, if it is not yet set up. After that,
              other Callable initialization actions are performed.
  
              :param init: value ``True`` is given when running this at the initialization phase. Then system
                           attribute is set already, but callable needs to be initialized otherwise.