code: def _fillna_prep(
      values, mask: npt.NDArray[np.bool_] | None = None
  ) -> npt.NDArray[np.bool_]:
      # boilerplate for _pad_1d, _backfill_1d, _pad_2d, _backfill_2d
  
      if mask is None:
          mask = isna(values)
  
      mask = mask.view(np.uint8)
      return mask
  
imports: from __future__ import annotations
  from functools import partial, wraps
  from typing import TYPE_CHECKING, Any, cast
  import numpy
  from pandas._libs import NaT, algos, lib
  from pandas._typing import ArrayLike, Axis, AxisInt, F, npt
  from pandas.compat._optional import import_optional_dependency
  from pandas.core.dtypes.cast import infer_dtype_from
  from pandas.core.dtypes.common import is_array_like, is_numeric_v_string_like, is_object_dtype, needs_i8_conversion
  from pandas.core.dtypes.missing import is_valid_na_for_dtype, isna, na_value_for_dtype
label_desc: Use image node_id 16 for calling a global function with example usage: _fillna_prep(values, mask) and returns: mask