GtkMenuShell::deselect
    
     As with the select_item()  
     method, deselect()  is mostly
     used internally.  A 'deselected' item is displayed in the normal state
     and has its submenu popped down, if it has one.
    
    
     Using this method causes the designated item to emit the 
     "deselect" signal, which in turn
     triggers the 'deselected' state.