docs: def initialize(self, conf, ctx):
          """Initialization steps:
  
          1. Prepare elasticsearch connection, including details for indexing.
          """
          config = get_config()['ElasticsearchIndexBolt']
          elasticsearch_class = import_name(config['elasticsearch_class'])
          self.es = elasticsearch_class(**config['elasticsearch_init'])
          self.index = config['index']
          self.doc_type = config['doc_type']