feat: add is_in to DaskExpr and mark is_duplicated and is_unique as not implemented

narwhals/_dask/expr.py

@@ -545,6 +545,22 @@ def func(_input: Any) -> Any:
             returns_scalar=False,
         )
 
+    def is_duplicated(self: Self) -> Self:
+        msg = "`Expr.is_duplicated` is not support since Dask currently has no native duplicated check"
+        raise NotImplementedError(msg)
+
+    def is_unique(self: Self) -> Self:
+        msg = "`Expr.is_duplicated` is not support since Dask currently has no native duplicated check"
+        raise NotImplementedError(msg)
+
+    def is_in(self: Self, other: Any) -> Self:
+        return self._from_call(
+            lambda _input, other: _input.isin(other),
+            "is_in",
+            other,
+            returns_scalar=False,
+        )
+
     def null_count(self: Self) -> Self:
         return self._from_call(
             lambda _input: _input.isna().sum(),

tests/expr_and_series/is_in_test.py

@@ -8,9 +8,7 @@
 data = {"a": [1, 4, 2, 5]}
 
 
-def test_expr_is_in(constructor: Any, request: Any) -> None:
-    if "dask" in str(constructor):
-        request.applymarker(pytest.mark.xfail)
+def test_expr_is_in(constructor: Any) -> None:
     df = nw.from_native(constructor(data))
     result = df.select(nw.col("a").is_in([4, 5]))
     expected = {"a": [False, True, False, True]}