code: def __init_yaml():
      
      global _yaml_initialized
      if not _yaml_initialized:
          _yaml_initialized = True
          yaml.add_constructor(u'tag:yaml.org,2002:Frame', _frame_constructor)
          yaml.add_constructor(u'tag:yaml.org,2002:Signal', _signal_constructor)
          yaml.add_representer(canmatrix.Frame, _frame_representer)
docs: Lazy init yaml because canmatrix might not be fully loaded when loading this format.