code: function _errorCb(err, result) {
  
            // if there is a conflict error, retrieve the document's revision first
            function _successCb(err, result) {
  
              // use the revision to update the existing documents
              // NOTE: it is not impossible that the revision of this document
              // is modified by other operations right before updating, Couchpenter
              // will only try once to avoid any possibility of retrying infinitely.
              doc._rev = result._rev;
              self.couch.use(dbName).insert(doc, self._handle(cb, {
                dbName: dbName,
                docId: doc._id,
                message: 'updated'
              }));
            }
  
            self.couch.use(dbName).get(doc._id, self._handle(cb, {
              dbName: dbName,
              docId: doc._id,
              successCb: _successCb
            }));
          }
docs: try to create documents, but with conflict error handling