private static TableDescriptorBuilder writeConstraint(TableDescriptorBuilder builder, String key,
    Configuration conf) throws IOException {
    // store the key and conf in the descriptor
    return builder.setValue(key, serializeConfiguration(conf));
  }
Write the given key and associated configuration to the {@link TableDescriptorBuilder}.
hbase-server/src/main/java/org/apache/hadoop/hbase/constraint/Constraints.java