code: def test_empty_list(self):
      joiner = DocumentJoiner()
      result = joiner.run([])
      assert result == {"documents": []}
  
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 3 for calling the TestDocumentJoiner obj's underlying member method code with example usage: obj.test_empty_list() without return types