code: def test_mlp_regressor_multi_identity(self):
      self._test_mlp_regressor(activation="identity")
  
imports: import unittest
  import warnings
  import numpy
  import torch
  from sklearn.neural_network import MLPClassifier, MLPRegressor
  import hummingbird.ml
  from hummingbird.ml import constants
  from hummingbird.ml._utils import tvm_installed
label_desc: Use image node_id 18 for calling the TestSklearnMLPClassifier obj's underlying member method code with example usage: obj.test_mlp_regressor_multi_identity() without return types