code: def test_serialize_cell(self):
      assert "foo" == self.db_hook._serialize_cell("foo", None)
  
imports: from __future__ import annotations
  import json
  from unittest import mock
  import pytest
  from airflow import models
  from airflow.providers.exasol.hooks.exasol import ExasolHook
label_desc: Use image node_id 12 for calling the TestExasolHook obj's underlying member method code with example usage: obj.test_serialize_cell() without return types