pyelasticsearch bulk ValueError: too many values to unpack (expected 2)

I'm new in Python and Elasticsearch. I'm trying to write code to insert documents in Elassticsearch using bulk. It is based on this description: http://pyelasticsearch.readthedocs.io/en/latest/api/#pyelasticsearch.ElasticSearch.bulk

My code:

>>> from pyelasticsearch import ElasticSearch
>>> es = ElasticSearch()
>>> es.bulk([es.index_op(doc={'id': 1, 'color': 'red'}), es.index_op(doc={'id': 2, 'color': 'green'})], doc_type='test10', index='test10')

Python returns this error message:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/fikfok/test_env/lib/python3.5/site-packages/pyelasticsearch/client.py", line 93, in decorate
    return func(*args, query_params=query_params, **kwargs)
  File "/home/fikfok/test_env/lib/python3.5/site-packages/pyelasticsearch/client.py", line 447, in bulk
    query_params=query_params)
  File "/home/fikfok/test_env/lib/python3.5/site-packages/pyelasticsearch/client.py", line 276, in send_request
    body=body)
ValueError: too many values to unpack (expected 2)

But it inserts these documents into Elasticsearch.

What I use:

Linux Mint 18.1
Elasticsearch 5.5.0 (engine)
virtualenv
Python 3.5.2
pyelasticsearch 1.4
elasticsearch 5.4.0 (package in virtual env "test_env")

Please tell me where I'm wrong and how to fix the error. Thanks!