code: def test_embed_metadata(self):
      embedder = SentenceTransformersDocumentEmbedder(
          model="model",
          meta_fields_to_embed=["meta_field"],
          embedding_separator="\n",
      )
      embedder.embedding_backend = MagicMock()
  
      documents = [
          Document(
              content=f"document number {i}",
              meta={"meta_field": f"meta_value {i}"},
          )
          for i in range(5)
      ]
  
      embedder.run(documents=documents)
  
      embedder.embedding_backend.embed.assert_called_once_with(
          [
              "meta_value 0\ndocument number 0",
              "meta_value 1\ndocument number 1",
              "meta_value 2\ndocument number 2",
              "meta_value 3\ndocument number 3",
              "meta_value 4\ndocument number 4",
          ],
          batch_size=32,
          show_progress_bar=True,
          normalize_embeddings=False,
      )
  
file_path: haystack/test/components/embedders/test_sentence_transformers_document_embedder.py
imports: from unittest.mock import patch, MagicMock
  import pytest
  import numpy
  from haystack import Document
  from haystack.components.embedders.sentence_transformers_document_embedder import SentenceTransformersDocumentEmbedder
label_desc: Use image node_id 9 for calling the TestSentenceTransformersDocumentEmbedder obj's underlying member method code with example usage: obj.test_embed_metadata() without return types