chore: Simplify polars .list.unique (#2946)

* chore: Simplify polars .list.unique

* refactor(typing): Remove unneeded `unique` annotation

#2946 (comment)

---------

Co-authored-by: dangotbanned <[email protected]>

Author: FBruzzesi

narwhals/_polars/expr.py

@@ -415,9 +415,6 @@ def len(self) -> PolarsExpr:
 
         return self.compliant._with_native(native_result)
 
-    def unique(self) -> PolarsExpr:
-        return self.compliant._with_native(self.native.list.unique())
-
 
 class PolarsExprStructNamespace(
     PolarsExprNamespace, PolarsStructNamespace[PolarsExpr, pl.Expr]

narwhals/_polars/series.py

@@ -737,11 +737,6 @@ def len(self) -> PolarsSeries:
         ns = self.__narwhals_namespace__()
         return self.to_frame().select(ns.col(name).list.len()).get_column(name)
 
-    def unique(self) -> PolarsSeries:
-        name = self.name
-        ns = self.__narwhals_namespace__()
-        return self.to_frame().select(ns.col(name).list.unique()).get_column(name)
-
 
 class PolarsSeriesStructNamespace(
     PolarsSeriesNamespace, PolarsStructNamespace[PolarsSeries, pl.Series]

narwhals/_polars/utils.py

@@ -333,13 +333,13 @@ class PolarsCatNamespace(PolarsAnyNamespace[CompliantT, NativeT_co]):
     get_categories: Method[CompliantT]
 
 
-# NOTE: Use `Protocol` if we **only** have defs to implement
-class PolarsListNamespace(
-    PolarsAnyNamespace[CompliantT_co, NativeT_co], Protocol[CompliantT_co, NativeT_co]
-):
+class PolarsListNamespace(PolarsAnyNamespace[CompliantT, NativeT_co]):
     _accessor: ClassVar[NativeAccessor] = "list"
 
-    def len(self) -> CompliantT_co: ...
+    @abc.abstractmethod
+    def len(self) -> CompliantT: ...
+
+    unique: Method[CompliantT]
 
 
 class PolarsStructNamespace(PolarsAnyNamespace[CompliantT, NativeT_co]):