get_transition_running
Description:
Gets whether a transition is currently running for this.
Note: 
      
        
    
    See [the migration guide](migrating-to-breakpoints.html#replace-adwsqueezer)
If a transition is impossible, the property value will be set to `TRUE` and then immediately to `FALSE`, so it's possible to rely on its notifications to know that a transition has happened.
Parameters:
| this | a squeezer | 
Returns:
| whether a transition is currently running |