code: def get_content (self):
          
          if self.data is None:
              log.debug(LOG_CHECK, "Get content of %r", self.url)
              t = time.time()
              self.data = self.read_content()
              self.size = len(self.data)
              self.dltime = time.time() - t
              if self.size == 0:
                  self.add_warning(_("Content size is zero."),
                               tag=WARN_URL_CONTENT_SIZE_ZERO)
              else:
                  self.aggregate.add_downloaded_bytes(self.size)
          return self.data
docs: Precondition: url_connection is an opened URL.