code: def test_trace(self):
      v = Variable(self.root)
      vname = str(v)
      trace = []
  
      def read_tracer(*args):
          trace.append(("read",) + args)
  
      def write_tracer(*args):
          trace.append(("write",) + args)
  
      tr1 = v.trace_add("read", read_tracer)
      tr2 = v.trace_add(["write", "unset"], write_tracer)
      self.assertEqual(
          sorted(v.trace_info()),
          [(("read",), tr1), (("write", "unset"), tr2)],
      )
      self.assertEqual(trace, [])
  
      v.set("spam")
      self.assertEqual(trace, [("write", vname, "", "write")])
  
      trace = []
      v.get()
      self.assertEqual(trace, [("read", vname, "", "read")])
  
      trace = []
      info = sorted(v.trace_info())
      v.trace_remove("write", tr1)  # Wrong mode
      self.assertEqual(sorted(v.trace_info()), info)
      with self.assertRaises(TclError):
          v.trace_remove("read", "spam")  # Wrong command name
      self.assertEqual(sorted(v.trace_info()), info)
      v.get()
      self.assertEqual(trace, [("read", vname, "", "read")])
  
      trace = []
      v.trace_remove("read", tr1)
      self.assertEqual(v.trace_info(), [(("write", "unset"), tr2)])
      v.get()
      self.assertEqual(trace, [])
  
      trace = []
      del write_tracer
      gc.collect()
      v.set("eggs")
      self.assertEqual(trace, [("write", vname, "", "write")])
  
      trace = []
      del v
      gc.collect()
      self.assertEqual(trace, [("write", vname, "", "unset")])
  
imports: import unittest
  from test import support
  import gc
  import tkinter
  from tkinter import Variable, StringVar, IntVar, DoubleVar, BooleanVar, Tcl, TclError
  from test.support import ALWAYS_EQ
  from test.test_tkinter.support import AbstractDefaultRootTest
label_desc: Use image node_id 11 for calling the TestVariable obj's underlying member method code with example usage: obj.test_trace() without return types