@Override
            @SuppressWarnings("unchecked")
            protected void writeTo(Output output, T message) throws IOException
            {
                final Map<Object, Enum<?>> existing = accessor.get(message);

                if (existing != null)
                    output.writeObject(number, existing, schema, false);
            }
Static utility for creating runtime {@link java.util.Map} fields.

@author David Yu
@created Jan 21, 2011
protostuff-runtime/src/main/java/io/protostuff/runtime/RuntimeMapFieldFactory.java