code: def test_empty_buffer(self):
      buffer = FifoReplayBuffer()
      batch = buffer.sample()
      self.assertEqual(len(batch), 0)
  
file_path: ray/python/ray/rllib/utils/replay_buffers/tests/test_fifo_replay_buffer.py
imports: import unittest
  import numpy
  from ray.rllib.policy.sample_batch import SampleBatch
  from ray.rllib.utils.replay_buffers.fifo_replay_buffer import FifoReplayBuffer
label_desc: Use image node_id 1 for calling the TestFifoReplayBuffer obj's underlying member method code with example usage: obj.test_empty_buffer() without return types