Example usage:
  ```python
  # Quantizing a model trained with QAT.
  quantization_options = tf.quantization.experimental.QuantizationOptions(
      signature_keys=['your_signature_key'],
  )
  tf.quantization.experimental.quantize_saved_model(
      '/tmp/input_model',
      '/tmp/output_model',
      quantization_options=quantization_options,
  )