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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 metadata(func):
 """Add metadata to an item. Decorator that adds metadata to a given item such as the gelk revision used. """

    @functools.wraps(func)
    def decorator(self, *args, **kwargs):
        eitem = func(self, *args, **kwargs)
        metadata = {
            'metadata__gelk_version': self.gelk_version,
            'metadata__gelk_backend_name': self.__class__.__name__,
            'metadata__enriched_on': datetime_utcnow().isoformat()
        }
        eitem.update(metadata)
        return eitem
    return decorator