code: protected TwoPhaseCommitSinkFunction<IN, TXN, CONTEXT> enableTransactionTimeoutWarnings(
  		double warningRatio) {
  		checkArgument(warningRatio >= 0 && warningRatio <= 1,
  			"warningRatio must be in range [0,1]");
  		this.transactionTimeoutWarningRatio = warningRatio;
  		return this;
  	}
docs: Enables logging of warnings if a transaction's elapsed time reaches a specified ratio of
  the <code>transactionTimeout</code>.
  If <code>warningRatio</code> is 0, a warning will be always logged when committing the
  transaction.
  
  @param warningRatio A value in the range [0,1].
  @return