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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def __init_yaml():
 """Lazy init yaml because canmatrix might not be fully loaded when loading this format."""

    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)