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

def add_lvl_to_ui(self, level, header):
        """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
        """
        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)