(s)
return "".join(i for i in s if i in TWITTER_CHARS)
normalize user input that is supposed to be a Twitter handle
normalize user input that is supposed to be a Twitter handle
normalize user input that is supposed to be a Twitter handle
def normalize_twitter(s):
    """normalize user input that is supposed to be a Twitter handle"""
    return "".join(i for i in s if i in TWITTER_CHARS)
def normalize_twitter ( s ) : return "" . join ( i for i in s if i in TWITTER_CHARS )