code: def set_url(self, url = None):
          
                  
          if url is None or type(url) is not str:
              raise KPError("Need a new image number")
          else:
              self.url = url
              self.last_mod = datetime.now().replace(microsecond=0)
              return True
docs: This method is used to set the url.
  
          url must be a string.