The code to obtain the following nice graph is too long to reproduce it here. Simply is there a way to remove the bounding box ?

|   | 1 |  initial version  | 
The code to obtain the following nice graph is too long to reproduce it here. Simply is there a way to remove the bounding box ?

 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.