Return a conll representation of a given input Extraction.

def extraction_to_conll(ex: Extraction) -> List[str]:
    """
    Return a conll representation of a given input Extraction.
    """
    ex = split_predicate(ex)
    toks = ex.sent.split(' ')
    ret = ['*'] * len(toks)
    args = [ex.arg1] + ex.args2
    rels_and_args = [("ARG{}".format(arg_ind), arg)
                     for arg_ind, arg in enumerate(args)] + \
                         [(rel_part.elem_type, rel_part)
                          for rel_part
                          in ex.rel]

    for rel, arg in rels_and_args:
        # Add brackets
        cur_start_ind = char_to_word_index(arg.span[0],
                                           ex.sent)
        cur_end_ind = char_to_word_index(arg.span[1],
                                         ex.sent)
        ret[cur_start_ind] = "({}{}".format(rel, ret[cur_start_ind])
        ret[cur_end_ind] += ')'
    return ret