def read_column_tagged_file(filename: str, tag_col: int = -1):
    """Reads column tagged (CONLL) style file (tab separated and token per line)
    tag_col is the column number to use as tag of the token (defualts to the last in line)
    return format :
    [ ['token', 'TAG'], ['token', 'TAG2'],... ]
    """
    data = []
    sentence = []
    labels = []
    with open(filename) as fp:
        for line in fp:
            line = line.strip()
            if len(line) == 0:
                if len(sentence) > 0:
                    data.append((sentence, labels))
                    sentence = []
                    labels = []
                continue
            splits = line.split()
            sentence.append(splits[0])
            labels.append(splits[tag_col])

    if len(sentence) > 0:
        data.append((sentence, labels))
    return data