code: def testGetFeatureValuesForModelSpecFieldNoValues(self):
      model_spec = config_pb2.ModelSpec(
          name="model1", example_weight_key="feature2"
      )
      extracts = {}
      got = model_util.get_feature_values_for_model_spec_field(
          [model_spec], "example_weight", "example_weights", extracts
      )
      self.assertIsNone(got)
  
imports: import tempfile
  import unittest
  from absl.testing import parameterized
  import apache_beam
  from apache_beam.testing import util
  import numpy
  import tensorflow
  from tensorflow_model_analysis import constants
  from tensorflow_model_analysis.api import types
  from tensorflow_model_analysis.eval_saved_model import testutil
  from tensorflow_model_analysis.proto import config_pb2
  from tensorflow_model_analysis.utils import model_util
  from tensorflow_model_analysis.utils import util
  from tfx_bsl.tfxio import tf_example_record
  from google.protobuf import text_format
  from tensorflow.core.protobuf import saved_model_pb2
  from tensorflow_metadata.proto.v0 import schema_pb2
label_desc: Use image node_id 15 for calling the ModelUtilTest obj's underlying member method code with example usage: obj.testGetFeatureValuesForModelSpecFieldNoValues() without return types