docstr: Test that sample will front pad segments.
docstr_tok: ["Test","that","sample","will","front","pad","segments","."]
code: def test_padding(self):
      """Test that sample will front pad segments."""
      for buffer_cls in (
          SegmentationBuffer,
          MultiAgentSegmentationBuffer,
      ):
          max_seq_len = 10
          max_ep_len = 100
          capacity = 1
          obs_dim = 3
          act_dim = 2
  
          buffer = buffer_cls(capacity, max_seq_len, max_ep_len)
  
          for ep_len in range(1, max_seq_len):
              # generate batch with episode lengths that are shorter than
              # max_seq_len to test padding.
              batch = _generate_episode_batch(
                  ep_len, 123, obs_dim, act_dim
              )
              buffer.add(batch)
  
              samples = _as_sample_batch(buffer.sample(50))
              for i in range(50):
                  # calculate number of pads based on the attention mask.
                  num_pad = int(
                      ep_len
                      - samples[SampleBatch.ATTENTION_MASKS][i].sum()
                  )
                  for key in samples.keys():
                      # make sure padding are added.
                      assert np.allclose(
                          samples[key][i, :num_pad], 0.0
                      ), "samples were not padded correctly."
  
imports: import unittest
  from typing import List, Union
  import numpy
  from rllib_dt.dt.segmentation_buffer import MultiAgentSegmentationBuffer, SegmentationBuffer
  import ray
  from ray.rllib.policy.sample_batch import DEFAULT_POLICY_ID, MultiAgentBatch, SampleBatch, concat_samples
  from ray.rllib.utils import test_utils
  from ray.rllib.utils.framework import try_import_tf, try_import_torch
  from ray.rllib.utils.typing import PolicyID
label_desc: Use image node_id 7 for calling the TestSegmentationBuffer obj's underlying member method code with example usage: obj.test_padding() without return types