code: def _rt_update_docindices(self, element, docstart, docend):
          
          #see how many characters have to be added/removed from the end
          #of the current doc limits.
          delta = element.docend - docend
          element.docstart = docstart
          element.docend = docend
          element.start += delta
          element.end += delta
  
          return delta
docs: Updates the docstart, docend, start and end attributes for the 
          specified element using the new limits for the docstring.