code: def _intf_ctrl(self):
          
  
          for key, val in self._ctrl.items():
              model, field, dest, astype = val
              self.copy_data_ext(
                  model, field, dest=dest, idx=self.__dict__[key], astype=astype)
docs: Retrieve variable indices of controlled models.
  
          Control interfaces are specified in ``self._ctrl``.
          Each ``key:value`` pair has ``key`` being the variable names
          for the reference idx and ``value`` being a tuple of
          ``(model name, field to read, destination field, return type)``.
  
          :Example:
  
              ``self._ctrl = {'syn', ('Synchronous', 'omega', 'w', list)}``
               - indices: self.syn
               - self.w = list(system.Synchronous.omega)
  
          :return: None