code: def test_while(self):
      source = """while a:
      b"""
      self.assertSame(source)
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import ast
  from ...asttools.visitors.pysourcegen import SourceGen
  from ...asttools.tests import AllTypesTested
  from ...testing import py2only, py3only
label_desc: Use image node_id 4 for calling the ControlFlow obj's underlying member method code with example usage: obj.test_while() without return types