Get answer's index of begin and end.

def get_answer_begin_end(data):
    '''
    Get answer's index of begin and end.
    '''
    begin = []
    end = []
    for qa_pair in data:
        tokens = qa_pair['passage_tokens']
        char_begin = qa_pair['answer_begin']
        char_end = qa_pair['answer_end']
        word_begin = get_word_index(tokens, char_begin)
        word_end = get_word_index(tokens, char_end)
        begin.append(word_begin)
        end.append(word_end)
    return np.asarray(begin), np.asarray(end)