code: def test_time_grain_expressions(
      time_grain: Optional[str], expected: str
  ) -> None:
      from superset.db_engine_specs.firebird import FirebirdEngineSpec
  
      assert (
          FirebirdEngineSpec._time_grain_expressions[time_grain].format(
              col="timestamp_column",
          )
          == expected
      )
  
file_path: superset/tests/unit_tests/db_engine_specs/test_firebird.py
imports: from datetime import datetime
  from typing import Optional
  import pytest
  from tests.unit_tests.db_engine_specs.utils import 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_time_grain_expressions(time_grain, expected) without return types