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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 example_yaml(cls, skip=()):
 """ Generate an example yaml string for a Serializable subclass. If traits have been tagged with an `example` value, then we use that value. Otherwise we fall back the default_value for the instance. """

        return cls.example_instance(skip=skip).to_yaml(skip=skip)