Adding an Elastic Search index to a Dataset
## Describe the bug
When trying to index documents from the squad dataset, the connection to ElasticSearch seems to break:

Reusing dataset squad (/Users/andreasmotz/.cache/huggingface/datasets/squad/plain_text/1.0.0/d6ec3ceb99ca480ce37cdd35555d6cb2511d223b9150cce08a837ef62ffea453)
 90%|████████████████████████████████████████████▉     | 9501/10570 [00:01<00:00, 6335.61docs/s]

No error is thrown, but the indexing breaks ~90%.

## Steps to reproduce the bug
```python
# Sample code to reproduce the bug
from datasets import load_dataset
from elasticsearch import Elasticsearch
es = Elasticsearch()
squad = load_dataset('squad', split='validation')
index_name = "corpus"
es_config = {
    "settings": {
        "number_of_shards": 1,
        "analysis": {"analyzer": {"stop_standard": {"type": "standard", " stopwords": "_english_"}}},
    },
    "mappings": {
        "properties": {
            "idx" : {"type" : "keyword"},
            "title" : {"type" : "keyword"},
            "text": {
                "type": "text",
                "analyzer": "standard",
                "similarity": "BM25"
            },
        }
    },
}
class IndexBuilder:
    """
    Elastic search indexing of a corpus
    """
    def __init__(
        self,
        *args,
        #corpus : None,
        dataset : squad,
        index_name = str,
        query = str,
        config = dict,
        **kwargs,
    ):
        #instantiate HuggingFace dataset
        self.dataset = dataset
        #instantiate ElasticSearch config
        self.config = config
        self.es = Elasticsearch()
        self.index_name = index_name
        self.query = query
    def elastic_index(self):
        print(self.es.info)
        self.es.indices.delete(index=self.index_name, ignore=[400, 404])
        search_index = self.dataset.add_elasticsearch_index(column='context', host='localhost', port='9200', es_index_name=self.index_name, es_index_config=self.config)
        return search_index
    def exact_match_method(self, index):
        scores, retrieved_examples = index.get_nearest_examples('context', query=self.query, k=1)
        return scores, retrieved_examples
if __name__ == "__main__":
    print(type(squad))
    Index = IndexBuilder(dataset=squad, index_name='corpus_index', query='Where was Chopin born?', config=es_config)
    search_index = Index.elastic_index()
    scores, examples = Index.exact_match_method(search_index)
    print(scores, examples)
    for name in squad.column_names:
        print(type(squad[name]))
```

## Environment info
We run the code in Poetry. This might be the issue, since the script runs successfully in our local environment.

Poetry:
- Python version: 3.8
- PyArrow: 4.0.1
- Elasticsearch: 7.13.4
- datasets: 1.10.2

Local:
- Python version: 3.8
- PyArrow: 3.0.0
- Elasticsearch: 7.7.1
- datasets: 1.7.0
