code: def _get_command_buffer(self, host_id, command_name):
          
          buf = self._cb_poll.get(host_id)
          if buf is not None:
              return buf
  
          if self._max_concurrency is not None:
              while len(self._cb_poll) >= self._max_concurrency:
                  self.join(timeout=1.0)
  
          def connect():
              return self.connection_pool.get_connection(
                  command_name, shard_hint=host_id)
          buf = CommandBuffer(host_id, connect, self.auto_batch)
          self._cb_poll.register(host_id, buf)
          return buf
docs: Returns the command buffer for the given command and arguments.