private <T> T getOrDefault(Bytes key, Function<byte[], T> function, T defaultValue) {
      Bytes value = values.get(key);
      if (value == null) {
        return defaultValue;
      } else {
        return function.apply(value.get());
      }
    }
Constructor. Makes a deep copy of the supplied descriptor. TODO: make this private after the
HCD is removed.
@param desc The descriptor.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/ColumnFamilyDescriptorBuilder.java