code: def test_empty(self):
      var1 = MyVariable("var1")
      var2 = MyVariable("var2")
      fg = FunctionGraph([var1, var2], [], clone=False)
      fg.check_integrity()
  
      assert fg.inputs == [var1, var2]
      assert fg.outputs == []
      assert not fg.variables
      assert not fg.apply_nodes
      assert fg.clients == {var1: [], var2: []}
  
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 24 for calling the TestFunctionGraph obj's underlying member method code with example usage: obj.test_empty() without return types