feat(typing): Add EagerNamespace._dataframe

Now we've got access to both `from_numpy` constructors from `Implementation`!

Author: dangotbanned

narwhals/_arrow/namespace.py

@@ -38,6 +38,10 @@
 
 
 class ArrowNamespace(EagerNamespace[ArrowDataFrame, ArrowSeries, ArrowExpr]):
+    @property
+    def _dataframe(self) -> type[ArrowDataFrame]:
+        return ArrowDataFrame
+
     @property
     def _expr(self) -> type[ArrowExpr]:
         return ArrowExpr

narwhals/_compliant/namespace.py

@@ -109,6 +109,8 @@ class EagerNamespace(
     DepthTrackingNamespace[EagerDataFrameT, EagerExprT],
     Protocol[EagerDataFrameT, EagerSeriesT, EagerExprT],
 ):
+    @property
+    def _dataframe(self) -> type[EagerDataFrameT]: ...
     @property
     def _series(self) -> type[EagerSeriesT]: ...
     def when(

narwhals/_pandas_like/namespace.py

@@ -34,6 +34,10 @@
 class PandasLikeNamespace(
     EagerNamespace[PandasLikeDataFrame, PandasLikeSeries, PandasLikeExpr]
 ):
+    @property
+    def _dataframe(self) -> type[PandasLikeDataFrame]:
+        return PandasLikeDataFrame
+
     @property
     def _expr(self) -> type[PandasLikeExpr]:
         return PandasLikeExpr