code: def session_id(self):
          
          return None if not self.session or 'JSESSIONID' not in \
              self.session.cookies else 'JSESSIONID={}'.format(
                  self.session.cookies['JSESSIONID'])
docs: The session ID in header type format. Can be inserted into a
          connection if necessary using::
          
              {'Cookie': session.session_id}
          
          :rtype: str