@Override
      public Boolean call(RegionObserver observer) throws IOException {
        return observer.preExists(this, get, getResult());
      }
Supports Coprocessor 'bypass'.
@param get the Get request
@return true or false to return to client if bypassing normal operation, or null otherwise
@exception IOException Exception
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionCoprocessorHost.java