Return unique mentions from a string.

get_mentions.py

def get_mentions(text):
    limits = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
    words = text.split()
    mentions = []
    for word in words:
        if word.endswith(('.', ',', '!', '?', ':', ';')):
            word = word[:-1]
        if word.endswith(')'):
            word = word[:-1]
        if word.startswith('('):
            word = word[1:]
        if word.startswith('@'):
            handle = word[1:]
            if handle and all(c in limits for c in handle):
                mentions.append(handle)
    return set(mentions)