def from_iob_to_io(sentences):
    """
    Transforms the IOB tags in sentences (output of create_sentences_out_of_dataframe) to IO tags
    :param sentences: (list of list of tuples)
    :return: (list of list of tuples)
    """
    clean_sentences=[]
    for desc in sentences:
        sublist=[]
        for x in desc:
            l = list(x)
            tag = l[1]
            if 'B-' in tag:
                tag = tag.replace('B-', '')
            elif 'I-' in tag:
                tag = tag.replace('I-', '')
            elif 'b-' in tag:
                tag = tag.replace('b-', '')
            elif 'i-' in tag:
                tag = tag.replace('i-', '')
            t = tuple([l[0], tag])
            sublist.append(t)
        clean_sentences.append(sublist)
    return clean_sentences