docstr: Test that the cache remains valid after reading/writing None.
docstr_tok: ["Test","that","the","cache","remains","valid","after","reading\/writing","None","."]
code: def test_example_proto_coder_cache(self):
      """Test that the cache remains valid after reading/writing None."""
      schema = schema_utils.schema_from_feature_spec(
          {
              "varlen": tf.io.VarLenFeature(tf.int64),
          }
      )
      coder = example_proto_coder.ExampleProtoCoder(schema)
      ascii_protos = [
          'features {feature {key: "varlen" value {int64_list {value: [5] }}}}',
          'features {feature {key: "varlen" value {}}}',
          'features {feature {key: "varlen" value {int64_list {value: [6] }}}}',
      ]
      instances = [{"varlen": [5]}, {"varlen": None}, {"varlen": [6]}]
      serialized_protos = map(_ascii_to_binary, ascii_protos)
      for instance, serialized_proto in zip(
          instances, serialized_protos
      ):
          self.assertSerializedProtosEqual(
              coder.encode(instance), serialized_proto
          )
  
imports: import copy
  import os
  import pickle
  import sys
  from absl import flags
  import numpy
  import tensorflow
  from tensorflow_transform.coders import example_proto_coder
  from tensorflow_transform import test_case
  from tensorflow_transform.tf_metadata import schema_utils
  from google.protobuf.internal import api_implementation
  from google.protobuf import text_format
label_desc: Use image node_id 7 for calling the ExampleProtoCoderTest obj's underlying member method code with example usage: obj.test_example_proto_coder_cache() without return types