code: def update(self, id, data):
          
          return json.loads(self._post(UrlEncoded(str(id)), headers=KVStoreCollectionData.JSON_HEADER, body=data).body.read().decode('utf-8'))
docs: Replaces document with _id = id with data.
  
          :param id: _id of document to update
          :type id: ``string``
          :param data: the new document to insert
          :type data: ``string``
  
          :return: id of replaced document
          :rtype: ``dict``