code: public void popContext ()
      {
          Context2 parentContext=currentContext.getParent();
          if(parentContext==null)
              throw new EmptyStackException();
          else
              currentContext = parentContext;
      }
docs: Revert to the previous Namespace context.
  
  <p>Normally, you should pop the context at the end of each
  XML element.  After popping the context, all Namespace prefix
  mappings that were previously in force are restored.</p>
  
  <p>You must not attempt to declare additional Namespace
  prefixes after popping a context, unless you push another
  context first.</p>
  
  @see #pushContext