code: def add_lvl_to_ui(self, level, header):
          
          lay = self.layout()
          rc = lay.rowCount()
          lay.addWidget(level, rc+1, 1)
          if header is not None:
              lay.addWidget(header, rc+1, 0)
          lay.setColumnStretch(1,1)
docs: Insert the level and header into the ui.
  
          :param level: a newly created level
          :type level: :class:`jukeboxcore.gui.widgets.browser.AbstractLevel`
          :param header: a newly created header
          :type header: QtCore.QWidget|None
          :returns: None
          :rtype: None
          :raises: None