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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 prepend(self, key, value, cas=0, format=None, persist_to=0, replicate_to=0):
 """Prepend a string to an existing value in Couchbase. .. seealso:: :meth:`append`, :meth:`prepend_multi` """

        return _Base.prepend(self, key, value, cas=cas, format=format,
                             persist_to=persist_to, replicate_to=replicate_to)