code: def test_multi_prop_callback_on_assignment_trace(self):
      # Register callback if either 'x' or 'y' changes on first trace
      fn = MagicMock()
      self.figure.data[0].on_change(fn, "x", "y")
  
      # Perform assignment on one of the properties
      self.figure.data[0].x = [11, 22, 33]
  
      # Check function called once with new value of x and old value of y
      fn.assert_called_once_with(
          self.figure.data[0], (11, 22, 33), (3, 2, 1)
      )
  
imports: import sys
  from unittest import TestCase
  import pytest
  import plotly.graph_objs
label_desc: Use image node_id 7 for calling the TestOnChangeCallbacks obj's underlying member method code with example usage: obj.test_multi_prop_callback_on_assignment_trace() without return types