to_file
Description:
This function saves the print settings from this to file_name.
If the file could not be written then error is set to either a `GFileError` or `GKeyFileError`.
Parameters:
| this | 
           a `GtkPrintSettings`  | 
      
| file_name | 
           the file to save to  | 
      
Returns:
| 
           true on success  |