code: def test_preprocess_input_symbolic_mixed_precision(self, mode):
      set_dtype_policy("mixed_float16")
      shape = (20, 20, 3)
      inputs = keras.layers.Input(shape=shape)
      try:
          keras.layers.Lambda(
              lambda x: utils.preprocess_input(x, mode=mode),
              output_shape=shape,
          )(inputs)
      finally:
          set_dtype_policy("float32")
  
file_path: keras/keras/applications/imagenet_utils_test.py
imports: import numpy
  import pytest
  from absl.testing import parameterized
  import keras
  from keras import backend
  from keras import testing
  from keras.applications import imagenet_utils
  from keras.mixed_precision import set_dtype_policy
label_desc: Use image node_id 3 for calling the TestImageNetUtils obj's underlying member method code with example usage: obj.test_preprocess_input_symbolic_mixed_precision(mode) without return types