code: def test_null_scalar(dtype):
      s = cudf.Scalar(None, dtype=dtype)
      if cudf.api.types.is_datetime64_dtype(
          dtype
      ) or cudf.api.types.is_timedelta64_dtype(dtype):
          assert s.value is cudf.NaT
      else:
          assert s.value is cudf.NA
      assert s.dtype == (
          cudf.dtype(dtype)
          if not isinstance(dtype, cudf.core.dtypes.DecimalDtype)
          else dtype
      )
      assert s.is_valid() is False
  
imports: import datetime
  import re
  from decimal import Decimal
  import numpy
  import pandas
  import pyarrow
  import pytest
  import rmm
  import cudf
  from cudf._lib.copying import get_element
  from cudf.testing._utils import ALL_TYPES, DATETIME_TYPES, NUMERIC_TYPES, TIMEDELTA_TYPES
label_desc: Use image node_id 6 for calling a global function with example usage: test_null_scalar(dtype) without return types