code: def fetch(self):
          
          if self.document_url is None:
              raise CloudantDocumentException(101)
          resp = self.r_session.get(self.document_url)
          resp.raise_for_status()
          self.clear()
          self.update(response_to_json_dict(resp, cls=self.decoder))
docs: Retrieves the content of the current document from the remote database
          and populates the locally cached Document object with that content.
          A call to fetch will overwrite any dictionary content currently in
          the locally cached Document object.