code: def put_http_connection(self, host, is_secure, conn):
          
          with self.mutex:
              key = (host, is_secure)
              if key not in self.host_to_pool:
                  self.host_to_pool[key] = HostConnectionPool()
              self.host_to_pool[key].put(conn)
docs: Adds a connection to the pool of connections that can be
          reused for the named host.