在下面的代码中，摘自文档：

package spendreport;

import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.walkthrough.common.sink.AlertSink;
import org.apache.flink.walkthrough.common.entity.Alert;
import org.apache.flink.walkthrough.common.entity.Transaction;
import org.apache.flink.walkthrough.common.source.TransactionSource;

public class FraudDetectionJob {

    public static void main(String[] args) throws Exception {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        DataStream<Transaction> transactions = env
            .addSource(new TransactionSource())
            .name("transactions");
        
        DataStream<Alert> alerts = transactions
            .keyBy(Transaction::getAccountId)
            .process(new FraudDetector())
            .name("fraud-detector");

        alerts
            .addSink(new AlertSink())
            .name("send-alerts");

        env.execute("Fraud Detection");
    }
}

应用于数据流transactions的.keyBy(Transaction::getAccountId)函数是否对传入数据进行分区（基于帐户ID），并在每个分区上执行process(new FraudDetector())，如下图所示？
2)如果是，如何写一个Map器来处理从每个分区流的数据？使用.keyBy(Transaction::getAccountId)？