code: protected synchronized <V> V retryRPC(RpcCallable<V> rpc) throws AlluxioStatusException {
      return retryRPCInternal(rpc, () -> null);
    }
docs: Tries to execute an RPC defined as a {@link RpcCallable}.
  
  If a {@link UnavailableException} occurs, a reconnection will be tried through
  {@link #connect()} and the action will be re-executed.
  
  @param rpc the RPC call to be executed
  @param <V> type of return value of the RPC call
  @return the return value of the RPC call