class documentation
        
        class NullDrawer(ShapeDrawer):
Static drawer class which draws nothing.
This class is used for graph vertices with unknown shapes
| Static Method | draw | Draws nothing. | 
| Class Variable | names | Undocumented | 
              Inherited from ShapeDrawer:
            
| Static Method | intersection | Determines where the shape centered at (center_x, center_y) intersects with a line drawn from (source_x, source_y) to (center_x, center_y). |