'Updates the list of shells.'

def append(self, location_a, location_b, shell_inst, ignore_type=False):

    if (not isinstance(shell_inst, Shell)):
        return
    shell_id = str(id(shell_inst))
    self.shell_tree.listholder[shell_id] = shell_inst
    try:
        shell_inst.identify_os()
        shell_show_str = str(shell_inst)
    except OSDetectionException:
        fmt = '<%s    object    (ruser:    "%s"    |    rsystem:    "%s")>'
        shell_show_str = (fmt % (shell_inst.get_name(), 'unknown', 'unknown'))
    gobject.idle_add(self.shell_tree.update_gui, shell_show_str, shell_id)
