code: def add_active_label(self, active_label):
          
  
          if not issubclass(active_label.__class__, Active_QLabel):
              raise foundations.exceptions.ProgrammingError("{0} | '{1}' must be a '{2}' subclass!".format(
                  self.__class__.__name__, active_label, Active_QLabel.__name__))
  
          if active_label in self.__active_labels:
              raise foundations.exceptions.ProgrammingError("{0} | '{1}' is already in the collection!".format(
                  self.__class__.__name__, active_label))
  
          active_label.checkable = True
          not self.__active_labels and active_label.set_checked(True) or active_label.set_checked(False)
          self.__active_labels.append(active_label)
  
          # Signals / Slots.
          active_label.toggled.connect(functools.partial(self.__active_label__toggled, active_label))
  
          active_label.clicked.connect(functools.partial(self.active_label_clicked.emit, active_label))
          active_label.pressed.connect(functools.partial(self.active_label_pressed.emit, active_label))
          active_label.released.connect(functools.partial(self.active_label_released.emit, active_label))
          active_label.toggled.connect(functools.partial(self.active_label_toggled.emit, active_label))
  
          return True
docs: Adds given **Active_QLabel** Widget.
  
          :param active_label: Active label to add.
          :type active_label: Active_QLabel
          :return: Method success.
          :rtype: bool