code: def test_attention(self):
      ds_spec = {
          "text": types.TextSegment(),
      }
      out_spec = {
          "tokens": types.Tokens(),
          "val": types.RegressionScore,
          "attn": types.AttentionHeads(
              align_in="tokens", align_out="tokens"
          ),
      }
      example = {"text": "hi"}
      output = {"tokens": ["hi"], "attn": np.array([[[0.1]], [[0.2]]])}
  
      attn = types.AttentionHeads(align_in="tokens", align_out="tokens")
      try:
          attn.validate_output(
              np.array([[[0.1]], [[0.2]]]),
              out_spec,
              output,
              ds_spec,
              ds_spec,
              example,
          )
      except ValueError:
          self.fail("Raised unexpected error.")
  
      self.assertRaises(
          ValueError,
          attn.validate_output,
          np.array([0.1, 0.2]),
          out_spec,
          output,
          ds_spec,
          ds_spec,
          example,
      )
  
      bad_attn = types.AttentionHeads(
          align_in="tokens", align_out="val"
      )
      self.assertRaises(
          ValueError,
          bad_attn.validate_output,
          np.array([[[0.1]], [[0.2]]]),
          out_spec,
          output,
          ds_spec,
          ds_spec,
          example,
      )
      bad_attn = types.AttentionHeads(
          align_in="val", align_out="tokens"
      )
      self.assertRaises(
          ValueError,
          bad_attn.validate_output,
          np.array([[[0.1]], [[0.2]]]),
          out_spec,
          output,
          ds_spec,
          ds_spec,
          example,
      )
  
imports: from collections.abc import Callable
  import os
  from typing import Any, Optional, Union
  from absl.testing import absltest
  from absl.testing import parameterized
  from etils import epath
  from lit_nlp.api import dtypes
  from lit_nlp.api import types
  import numpy
label_desc: Use image node_id 20 for calling the TypesTest obj's underlying member method code with example usage: obj.test_attention() without return types