Given a list of extractions for a single sentence -
    convert it to conll representation.

def convert_sent_to_conll(sent_ls: List[Extraction]):
    """
    Given a list of extractions for a single sentence -
    convert it to conll representation.
    """
    # Sanity check - make sure all extractions are on the same sentence
    assert(len(set([ex.sent for ex in sent_ls])) == 1)
    toks = sent_ls[0].sent.split(' ')

    return safe_zip(*[range(len(toks)),
                      toks] + \
                    [extraction_to_conll(ex)
                     for ex in sent_ls])