code: def _add_nnpack(self, net):
      transformer.AddNNPACK(net)
      assert tu.str_compare(net.Proto().op[0].engine, "NNPACK")
  
imports: from hypothesis import given
  import hypothesis.strategies
  import numpy
  import unittest
  from caffe2.python.transformations import Transformer
  from caffe2.python import core, workspace
  from caffe2.python import test_util
label_desc: Use image node_id 2 for calling the TestTransformations obj's underlying member method code with example usage: obj._add_nnpack(net) without return types