code: def get_versions(source):
      
      tree = compiler.parse(source)
      checker = compiler.walk(tree, NodeChecker())
      return checker.vers
docs: Return information about the Python versions required for specific features.
  
      The return value is a dictionary with keys as a version number as a tuple
      (for example Python 2.6 is (2,6)) and the value are a list of features that
      require the indicated Python version.