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
        """
        w = QtGui.QWidget(self)
        vbox = QtGui.QVBoxLayout()
        vbox.setContentsMargins(0, 0, 0, 0)
        w.setLayout(vbox)
        if header is not None:
            vbox.addWidget(header)
        vbox.addWidget(level)
        self.splitter.addWidget(w)