':param int cid: è¯è®ºID
:param int group_id: è¯è®ºæåšçç»ID
:param Answer answer: è¯è®ºæåšçç­æ¡å¯¹è±¡
:param Author author: è¯è®ºçäœèå¯¹è±¡
:param int upvote_num: è¯è®ºèµåæ°é
:param str content: è¯è®ºåå®¹
:param datetime.datetime creation_time: è¯è®ºåè¡šæ¶éŽ
:return: è¯è®ºå¯¹è±¡
:rtype: Comment'

def __init__(self, cid, answer, author, upvote_num, content, time, group_id=None):

    self.cid = cid
    self.answer = answer
    self.author = author
    self.upvote_num = upvote_num
    self.content = content
    self.creation_time = time
    self._group_id = group_id
