get_file
Description:
Returns the file that this is currently playing from.
When this is not playing or not playing from a file, null is returned.
Parameters:
| this | 
           a `GtkMediaFile`  | 
      
Returns:
| 
           The currently playing file  | 
      
Returns the file that this is currently playing from.
When this is not playing or not playing from a file, null is returned.
| this | 
           a `GtkMediaFile`  | 
      
| 
           The currently playing file  |