@Override
        public void putExtraOption(String key, Object value)
        {
            if (extraOptions.put(key, value) != null)
                throw err("Duplicate rpc option: " + key, getProto());
        }
Represents a service defined in the proto (for generating rpc services).

@author David Yu
@created Jun 18, 2010
protostuff-parser/src/main/java/io/protostuff/parser/Service.java