code: def fillna(
      self, value, limit: int | None, inplace: bool, downcast
  ) -> Self:
      if limit is not None:
          # Do this validation even if we go through one of the no-op paths
          limit = libalgos.validate_limit(None, limit=limit)
  
      return self.apply_with_block(
          "fillna",
          value=value,
          limit=limit,
          inplace=inplace,
          downcast=downcast,
          using_cow=using_copy_on_write(),
          already_warned=_AlreadyWarned(),
      )
  
imports: from __future__ import annotations
  from typing import TYPE_CHECKING, Any, Literal, cast, final
  import numpy
  from pandas._config import using_copy_on_write, warn_copy_on_write
  from pandas._libs import algos, lib
  from pandas.errors import AbstractMethodError
  from pandas.util._validators import validate_bool_kwarg
  from pandas.core.dtypes.cast import find_common_type, np_can_hold_element
  from pandas.core.dtypes.dtypes import ExtensionDtype, SparseDtype
  from pandas.core.base import PandasObject
  from pandas.core.construction import extract_array
  from pandas.core.indexes.api import Index, default_index
label_desc: Use image node_id 13 for calling the DataManager obj's underlying member method code with example usage: obj.fillna(value, limit, inplace, downcast) and returns: self