get_frame
  
  Description:
  public unowned Frame get_frame ()
  
 
  
    Returns a Frame object suitable to render the current frame of the given 
      video sink.
     An application is free to make a copy of this pipeline and modify it for custom rendering.
    Parameters:
    
    Returns:
    
      
        | A Frame or NULL if there  isn't a frame to be displayed yet. |