code: def test_to_shape_proto_unspecified():
      shape = (28, 28, None)
      shape_proto = feature.to_shape_proto(shape)
      assert shape_proto.dimensions == [28, 28, -1]
  
imports: import numpy
  import pytest
  import tensorflow
  from tensorflow_datasets.core.features import feature
  from tensorflow_datasets.core.features import image_feature
  from tensorflow_datasets.core.proto import feature_pb2
label_desc: Use image node_id 4 for calling a global function with example usage: test_to_shape_proto_unspecified() without return types