@InterfaceAudience.Private
  public String getScanAsString() {
    return this.scan;
  }
Returns a scan string
@return scan as string. Should be noted that this is not same as getScan().toString() because
        Scan object will have the default values when empty scan string is deserialized. Thus,
        getScan().toString() can never be empty
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableSplit.java