@Override
    public void putExtraOption(String key, Object value)
    {
        if (extraOptions.put(key, value) != null)
            throw err("Duplicate service 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