code: def test_serialize(self):
      payload = {
          "metadatabase": {"status": "healthy"},
          "scheduler": {
              "status": "healthy",
              "latest_scheduler_heartbeat": self.default_datetime,
          },
      }
      serialized_data = health_schema.dump(payload)
      assert serialized_data == payload
  
imports: from __future__ import annotations
  from airflow.api_connexion.schemas.health_schema import health_schema
label_desc: Use image node_id 2 for calling the TestHealthSchema obj's underlying member method code with example usage: obj.test_serialize() without return types