Reply_count attribute missing from tweet object



I am trying to retrieve the count of replies for a particular tweet(using tweet.retweet_count). But I am getting attribute not found error. Seems this attribute is missing from the tweet object.But when I check in the documentation of tweet object, its listed and should have been available. Am I mssing something?

documentation -

I am using python and following is my code:
api = tweepy.API(auth)
alltweets = api.user_timeline(screen_name = screen_name,count=200)
for tweet in alltweets:
outtweets.append([tweet.id_str, tweet.reply_count,tweet.retweet_count,tweet.favorite_count,tweet.retweeted,tweet.lang])


See New Tweet updates - reply_count