code: def test_flatten_metadata():
      data = {
          "inputs": {"text": "bogh"},
          "metadata": {
              "mail": {
                  "subject": "The mail subject",
                  "body": "This is a large text body",
              }
          },
      }
      record = ServiceTextClassificationRecord.parse_obj(data)
      assert list(record.metadata.keys()) == [
          "mail.subject",
          "mail.body",
      ]
  
imports: import pytest
  from argilla.server.apis.v0.models.text_classification import TextClassificationAnnotation, TextClassificationQuery, TextClassificationRecord
  from argilla.server.commons.models import PredictionStatus, TaskStatus
  from argilla.server.daos.backend.search.query_builder import EsQueryBuilder
  from argilla.server.services.tasks.text_classification.model import ClassPrediction, ServiceTextClassificationRecord
  from tests.pydantic_v1 import ValidationError
label_desc: Use image node_id 1 for calling a global function with example usage: test_flatten_metadata() without return types