session_monitor_start
Description:
public async bool session_monitor_start (Parent? parent, SessionMonitorFlags flags, Cancellable? cancellable) throws Error
  
  Makes [class@Portal] start monitoring the login session state.
When the state changes, the [signal@Portal:XdpPortal:session-state-changed] signal is emitted.
Use [method@Portal.session_monitor_stop] to stop monitoring.
Parameters:
| this | 
           a [class@Portal]  | 
      
| parent | 
           a XdpParent, or `NULL`  | 
      
| flags | 
           options for this call  | 
      
| cancellable | 
           optional [class@Gio.Cancellable]  | 
      
| callback | 
           a callback to call when the request is done  | 
      
| data | 
           data to pass to   |