code: def test_source_id_stored_in_metadata(self):
      splitter = DocumentSplitter(split_by="word", split_length=10)
      doc1 = Document(content="This is a text with some words.")
      doc2 = Document(
          content="This is a different text with some words."
      )
      result = splitter.run(documents=[doc1, doc2])
      assert result["documents"][0].meta["source_id"] == doc1.id
      assert result["documents"][1].meta["source_id"] == doc2.id
  
file_path: haystack/test/components/preprocessors/test_document_splitter.py
imports: import pytest
  from haystack import Document
  from haystack.components.preprocessors import DocumentSplitter
label_desc: Use image node_id 12 for calling the TestDocumentSplitter obj's underlying member method code with example usage: obj.test_source_id_stored_in_metadata() without return types