add: literal type hints for methods in NDFrame (#52724)

* add: literal type hints

* review comments

Author: YYYasin19

pandas/core/generic.py

@@ -2126,7 +2126,7 @@ def to_excel(
         index_label: IndexLabel = None,
         startrow: int = 0,
         startcol: int = 0,
-        engine: str | None = None,
+        engine: Literal["openpyxl", "xlsxwriter"] | None = None,
         merge_cells: bool_t = True,
         inf_rep: str = "inf",
         freeze_panes: tuple[int, int] | None = None,
@@ -2273,7 +2273,8 @@ def to_excel(
     def to_json(
         self,
         path_or_buf: FilePath | WriteBuffer[bytes] | WriteBuffer[str] | None = None,
-        orient: str | None = None,
+        orient: Literal["split", "records", "index", "table", "columns", "values"]
+        | None = None,
         date_format: str | None = None,
         double_precision: int = 10,
         force_ascii: bool_t = True,
@@ -11520,7 +11521,7 @@ def rolling(
         win_type: str | None = None,
         on: str | None = None,
         axis: Axis | lib.NoDefault = lib.no_default,
-        closed: str | None = None,
+        closed: IntervalClosedType | None = None,
         step: int | None = None,
         method: str = "single",
     ) -> Window | Rolling:
@@ -11579,7 +11580,7 @@ def expanding(
         self,
         min_periods: int = 1,
         axis: Axis | lib.NoDefault = lib.no_default,
-        method: str = "single",
+        method: Literal["single", "table"] = "single",
     ) -> Expanding:
         if axis is not lib.no_default:
             axis = self._get_axis_number(axis)
@@ -11617,7 +11618,7 @@ def ewm(
         ignore_na: bool_t = False,
         axis: Axis | lib.NoDefault = lib.no_default,
         times: np.ndarray | DataFrame | Series | None = None,
-        method: str = "single",
+        method: Literal["single", "table"] = "single",
     ) -> ExponentialMovingWindow:
         if axis is not lib.no_default:
             axis = self._get_axis_number(axis)