public static ObjectAllocator XML_PROCESSING_INSTRUCTION_ALLOCATOR = new ObjectAllocator()
  {
    private XmlProcessingInstruction xmlProcessingInstruction = null;
    public IRubyObject allocate(Ruby runtime, RubyClass klazz) {
      if (xmlProcessingInstruction == null) { xmlProcessingInstruction = new XmlProcessingInstruction(runtime, klazz); }