code: def test_simple_dtype_init_returns_instance() -> None:
      dtype = pl.Int8()
      assert isinstance(dtype, pl.Int8)
  
file_path: polars/py-polars/tests/unit/test_datatypes.py
imports: from __future__ import annotations
  import pickle
  from datetime import datetime, timedelta
  from typing import TYPE_CHECKING
  import pytest
  import polars
  from polars import datatypes
  from polars.datatypes import DTYPE_TEMPORAL_UNITS, DataTypeGroup, Field, Int64, List, Struct, py_type_to_dtype
label_desc: Use image node_id 2 for calling a global function with example usage: test_simple_dtype_init_returns_instance() without return types