docs: def mousePressEvent( self, event ):
          """
          Overloads the base QGraphicsScene method to block the \
          selection signals, otherwise, each time an object is \
          bulk selected the selection changed signal will be \
          emitted.
                      
          :param      event   <QMousePressEvent>
          """
          if event.button() == Qt.MidButton:
              self.setViewMode(True)
              event.accept()
          elif event.button() == Qt.RightButton:
              event.accept()
          else:
              super(XNodeScene, self).mousePressEvent(event)
              self.blockSelectionSignals(True)