code: def test_extract_features(self):
      encoder = self._small_encoder()
      tokens = torch.LongTensor([5, 10, 20])
      encoder.extract_features(tokens)
  
file_path: pytext/pytext/models/representations/test/transformer_test.py
imports: import unittest
  import torch
  from pytext.models.representations.transformer import MultiheadSelfAttention, SentenceEncoder, Transformer, TransformerLayer
  from pytext.models.representations.transformer.representation import TransformerRepresentation
label_desc: Use image node_id 2 for calling the SentenceEncoderTest obj's underlying member method code with example usage: obj.test_extract_features() without return types