def return_in_nltk_format_unique(file):
    """Return the tagged tokens from unique files (such as train.txt) as list of tuples in the form (token, tag)"""
    sequences = []
    with open(file, 'r') as training_file:
        articles = training_file.read().split('\n\n')
        for article in articles:
            lines = [tuple(x.split('\t')) for x in article.splitlines()]
            lines = list(filter(lambda x: len(x) == 2, lines))
            sequences.append(lines)
    return sequences[:-2]