message: Do not raise error for non-op models in modifying i/o types.
diff: @@ -651,7 +651,7 @@ def _modify_model_input_type(model, inference_input_type=dtypes.float32):
  builtin_code = schema_util.get_builtin_code_from_operator_code(opcode)
  if builtin_code == schema_fb.BuiltinOperator.QUANTIZE:
  quant_opcode_idxs.append(idx)
  - if not quant_opcode_idxs:
  + if operators and not quant_opcode_idxs:
  raise ValueError("Model input is not quantized.")
  # Validate that the model input is quantized
  @@ -736,7 +736,7 @@ def _modify_model_output_type(model, inference_output_type=dtypes.float32):
  builtin_code = schema_util.get_builtin_code_from_operator_code(opcode)
  if builtin_code == schema_fb.BuiltinOperator.DEQUANTIZE:
  dequant_opcode_idxs.append(idx)
  - if not dequant_opcode_idxs:
  + if operators and not dequant_opcode_idxs:
  raise ValueError("Model output is not dequantized.")
  # Validate that the model output is dequantized
  