def find_master_tab(self,tab,as_list=False):
        """
        Try to return the frontend that owns the kernel attached to the given widget/tab.

            Only finds frontend owned by the current application. Selection
            based on port of the kernel might be inaccurate if several kernel
            on different ip use same port number.

            This function does the conversion tabNumber/widget if needed.
            Might return None if no master widget (non local kernel)
            Will crash IPython if more than 1 masterWidget

            When asList set to True, always return a list of widget(s) owning
            the kernel. The list might be empty or containing several Widget.
        """

        #convert from/to int/richIpythonWidget if needed
        if isinstance(tab, int):
            tab = self.tab_widget.widget(tab)
        km=tab.kernel_manager

        #build list of all widgets
        widget_list = [self.tab_widget.widget(i) for i in range(self.tab_widget.count())]

        # widget that are candidate to be the owner of the kernel does have all the same port of the curent widget
        # And should have a _may_close attribute
        filtered_widget_list = [ widget for widget in widget_list if
                                widget.kernel_manager.connection_file == km.connection_file and
                                hasattr(widget,'_may_close') ]
        # the master widget is the one that may close the kernel
        master_widget= [ widget for widget in filtered_widget_list if widget._may_close]
        if as_list:
            return master_widget
        assert(len(master_widget)<=1 )
        if len(master_widget)==0:
            return None

        return master_widget[0]
Try to return the frontend that owns the kernel attached to the given widget/tab.

            Only finds frontend owned by the current application. Selection
            based on port of the kernel might be inaccurate if several kernel
            on different ip use same port number.

            This function does the conversion tabNumber/widget if needed.
            Might return None if no master widget (non local kernel)
            Will crash IPython if more than 1 masterWidget

            When asList set to True, always return a list of widget(s) owning
            the kernel. The list might be empty or containing several Widget.