code: def test_for_unpack(self):
      source = "for i, j in a:\n    x += b[i]"
      self.assertDepends(
          source,
          {
              ("i", "a"),
              ("j", "a"),
              ("b", "a"),
              ("x", "a"),
              ("x", "i"),
              ("x", "b"),
              ("x", "x"),
          },
          {"a", "b"},
          {"x", "i", "j"},
      )
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import ast
  from ...asttools.visitors.graph_visitor import GraphGen
  from ...asttools.visitors.graph_visitor import DiGraph
  from ...asttools.tests import AllTypesTested, skip_networkx
label_desc: Use image node_id 20 for calling the Test obj's underlying member method code with example usage: obj.test_for_unpack() without return types