private static String asSeparateLines(String keyValueStr) {
    return keyValueStr.replaceAll(", ([a-zA-Z]+=)", ",\n" + FOUR_SPACES + "$1");
  }
Format a string of the form "k1=v1, k2=v2, ..." into separate lines with a four-space
indentation.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePrettyPrinter.java