code: def _get_agent_key(self, proxy=None):
          
          if self._proxy is None:
              self._proxy = proxy
          if self._proxy is not None and self._proxy.has_effective_agent():
              agent_key = self._proxy.get_effective_agent_id()
          else:
              agent_key = None
          if agent_key not in self._provider_sessions:
              self._provider_sessions[agent_key] = dict()
          return agent_key
docs: Gets an agent key for session management.
  
          Side effect of setting a new proxy if one is sent along,
          and initializing the provider session map if agent key has
          not been seen before