def write_example_yaml(cls, dest, skip=()):
        """
        Write a file containing an example yaml string for a Serializable
        subclass.
        """
        # Make sure we can make an instance before we open a file.
        inst = cls.example_instance(skip=skip)
        with open(dest, 'w') as f:
            inst.to_yaml(stream=f, skip=skip)