code: def test_convert_dttm(
      target_type: str, expected_result: Optional[str], dttm: datetime
  ) -> None:
      from superset.db_engine_specs.postgres import (
          PostgresEngineSpec as spec,
      )
  
      assert_convert_dttm(spec, target_type, expected_result, dttm)
  
file_path: superset/tests/unit_tests/db_engine_specs/test_postgres.py
imports: from datetime import datetime
  from typing import Any, Optional
  import pytest
  from pytest_mock import MockFixture
  from sqlalchemy import types
  from sqlalchemy.dialects.postgresql import DOUBLE_PRECISION, ENUM, JSON
  from sqlalchemy.engine.url import make_url
  from superset.exceptions import SupersetSecurityException
  from superset.utils.core import GenericDataType
  from tests.unit_tests.db_engine_specs.utils import assert_column_spec, assert_convert_dttm
  from tests.unit_tests.fixtures.common import dttm
label_desc: Use image node_id 1 for calling a global function with example usage: test_convert_dttm(target_type, expected_result, dttm) without return types