code: def test_assignment_across_modules(self):
      B = ContextVar("B", 1)
      # local assignment
      B.value = 2
      self.assertEqual(B.value, 2)
      # Assignment in another module.
      exec(
          'from tinygrad.helpers import ContextVar;B = ContextVar("B", 0);B.value = 3;',
          {},
      )  # pylint:disable=exec-used
      # Assignment in another module should affect this one as well.
      self.assertEqual(B.value, 3)
  
imports: import unittest
  from PIL import Image
  from tinygrad.helpers import Context, ContextVar, merge_dicts, strip_parens, prod, round_up, fetch, fully_flatten, from_mv, to_mv
  from tinygrad.shape.symbolic import Variable, NumNode
label_desc: Use image node_id 7 for calling the TestContextVars obj's underlying member method code with example usage: obj.test_assignment_across_modules() without return types