code: def test_pickle(self):
      var1 = op1()
      var2 = op2()
      var3 = op1(var1)
      var4 = op2(var3, var2)
      func = FunctionGraph([var1, var2], [var4])
  
      s = pickle.dumps(func)
      new_func = pickle.loads(s)
  
      assert all(
          type(a) == type(b)
          for a, b in zip(func.inputs, new_func.inputs)
      )
      assert all(
          type(a) == type(b)
          for a, b in zip(func.outputs, new_func.outputs)
      )
      assert all(
          type(a.op) is type(b.op)  # noqa: E721
          for a, b in zip(func.apply_nodes, new_func.apply_nodes)
      )
      assert all(
          a.type == b.type
          for a, b in zip(func.variables, new_func.variables)
      )
  
imports: import pickle
  import numpy
  import pytest
  from pytensor.configdefaults import config
  from pytensor.graph.basic import NominalVariable
  from pytensor.graph.fg import FunctionGraph
  from pytensor.graph.utils import MissingInputError
  from tests.graph.utils import MyConstant, MyOp, MyType, MyVariable, MyVariable2, op1, op2, op3
label_desc: Use image node_id 1 for calling the TestFunctionGraph obj's underlying member method code with example usage: obj.test_pickle() without return types