get_fraction
Description:
Returns the current fraction of the task that’s been completed.
Parameters:
| this | 
           a `GtkProgressBar`  | 
      
Returns:
| 
           a fraction from 0.0 to 1.0  | 
      
Returns the current fraction of the task that’s been completed.
| this | 
           a `GtkProgressBar`  | 
      
| 
           a fraction from 0.0 to 1.0  |