@Override
  public byte[] toByteArray() {
    FilterProtos.MultipleColumnPrefixFilter.Builder builder =
      FilterProtos.MultipleColumnPrefixFilter.newBuilder();
    for (byte[] element : sortedPrefixes) {
      if (element != null) builder.addSortedPrefixes(UnsafeByteOperations.unsafeWrap(element));
    }
    return builder.build().toByteArray();
  }
Returns The filter serialized using pb
hbase-client/src/main/java/org/apache/hadoop/hbase/filter/MultipleColumnPrefixFilter.java