changed str to literal in inteprolate and limit_direction (#52755)

changed it to literal

Author: VanMyHu

pandas/core/generic.py

@@ -7497,12 +7497,32 @@ def replace(
 
     def interpolate(
         self,
-        method: str = "linear",
+        method: Literal[
+            "linear",
+            "time",
+            "index",
+            "values",
+            "pad",
+            "nearest",
+            "zero",
+            "slinear",
+            "quadratic",
+            "cubic",
+            "barycentric",
+            "polynomial",
+            "krogh",
+            "piecewise_polynomial",
+            "spline",
+            "pchip",
+            "akima",
+            "cubicspline",
+            "from_derivatives",
+        ] = "linear",
         *,
         axis: Axis = 0,
         limit: int | None = None,
         inplace: bool_t = False,
-        limit_direction: str | None = None,
+        limit_direction: Literal["forward", "backward", "both"] | None = None,
         limit_area: str | None = None,
         downcast: str | None = None,
         **kwargs,