code: def test_method(self):
      x = 1
  
      class Foo:
          def f(self):
              return x
  
      foo = Foo()
      func_map = free_vars_detect._detect_function_free_vars(foo.f)
      self.assertLen(func_map.keys(), 1)
      self.assertIn("Foo.f", func_map.keys())
      free_vars = get_var_name(func_map["Foo.f"])
      self.assertSequenceEqual(free_vars, ["x"])
  
imports: import functools
  import unittest
  from absl.testing import parameterized
  import numpy
  from tensorflow.core.function.capture import free_vars_detect
  from tensorflow.python.util import tf_decorator
label_desc: Use image node_id 16 for calling the FreeVarDetectionTest obj's underlying member method code with example usage: obj.test_method() and returns: x