AttributeError: 'HTTPHeaderDict' object has no attribute 'get_all' while mapping the mappings in elasticsearch

Here I have added my code:

from datetime import datetime
from elasticsearch_dsl import Document, Date, Integer, Keyword, Text
from elasticsearch_dsl.connections import connections

# Define a default Elasticsearch client
connections.create_connection(hosts=['localhost'])

class Article(Document):
    title = Text(analyzer='snowball', fields={'raw': Keyword()})
    body = Text(analyzer='snowball')
    tags = Keyword()
    published_from = Date()
    lines = Integer()

    class Index:
        name = 'blog'
        settings = {
          "number_of_shards": 2,
        }

    def save(self, ** kwargs):
        self.lines = len(self.body.split())
        return super(Article, self).save(** kwargs)

    def is_published(self):
        return datetime.now() >= self.published_from

# create the mappings in elasticsearch
Article.init()

Here I am adding my elasticsearch and elasticsearch_dsl versions:

1. elasticsearch==7.8.0
2. elasticsearch_dsl==7.0.0

The error I have got from the code:

AttributeError: 'HTTPHeaderDict' object has no attribute 'get_all'

Please help me!