import string


def clean_tokens(sequence):
    """
    This function removes the following:
     1. All empty tokens
     2. Remove punctuations from the words
    :param sequence:
    :return:
    """
    table = str.maketrans('', '', string.punctuation)
    sequence = [x.lower() for x in sequence]
    sequence = [x.translate(table) for x in sequence]
    sequence = [x for x in sequence if x.isalpha()]
    return list(filter(lambda a: a not in ['', ' '], sequence))