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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 set(self, key, value, lease=None, return_previous=None, timeout=None):
 """ Set the value for the key in the key-value store. Setting a value on a key increments the revision of the key-value store and generates one event in the event history. :param key: key is the key, in bytes, to put into the key-value store. :type key: bytes :param value: value is the value, in bytes, to associate with the key in the key-value store. :key value: bytes :param lease: Lease to associate the key in the key-value store with. :type lease: instance of :class:`txaioetcd.Lease` or None :param return_previous: If set, return the previous key-value. :type return_previous: bool or None :param timeout: Request timeout in seconds. :type timeout: int :returns: Revision info :rtype: instance of :class:`txaioetcd.Revision` """

        assembler = commons.PutRequestAssembler(self._url, key, value, lease, return_previous)

        obj = yield self._post(assembler.url, assembler.data, timeout)

        revision = Revision._parse(obj)

        returnValue(revision)