[jfml]

I used following codes to get a file which contains all contacts information in my mobile phone's Contacts Book:
def listContactInformations(self):
self.__openFile()
db = contacts.open()
self.__file.write(str(dir(db)))
self.__file.write('\n')
for entry_id in db:
contact = db[entry_id]
self.__file.write("[ID] - " + str(contact.id))
self.__file.write('\t')
self.__file.write("[TITLE] - " + contact.title.encode(CODEC_UTF8))
self.__file.write('\t')
self.__file.write("[ISGROUP] - " + str(contact.is_group))
self.__file.write('\t')
But I found that the result of this file just conatins all Contact information but not any Group information. Every "contact" object's field "is_group" return value "0" which means it's just a normal contact. Does anyone know how can I get the group list in Contacts Book?