code: def test_init(self):
      joiner = DocumentJoiner()
      assert joiner.join_mode == "concatenate"
      assert joiner.weights is None
      assert joiner.top_k is None
      assert joiner.sort_by_score
  
file_path: haystack/test/components/joiners/test_document_joiner.py
imports: import logging
  import pytest
  from haystack import Document
  from haystack.components.joiners.document_joiner import DocumentJoiner
label_desc: Use image node_id 1 for calling the TestDocumentJoiner obj's underlying member method code with example usage: obj.test_init() without return types