code: def channel_choice_control(self):
          
          self.current.task_data['control'], self.current.task_data['msg'] \
              = self.selection_error_control(self.input['form'])
          if self.current.task_data['control']:
              self.current.task_data['option'] = self.input['cmd']
              self.current.task_data['split_operation'] = False
              keys, names = self.return_selected_form_items(self.input['form']['ChannelList'])
              self.current.task_data['chosen_channels'] = keys
              self.current.task_data['chosen_channels_names'] = names
docs: It controls errors. If there is an error,
          returns channel list screen with error message.