done

lib/python3.11/site-packages/narwhals/_arrow/series_cat.py

@@ -0,0 +1,18 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import pyarrow as pa
+
+from narwhals._arrow.utils import ArrowSeriesNamespace
+
+if TYPE_CHECKING:
+    from narwhals._arrow.series import ArrowSeries
+    from narwhals._arrow.typing import Incomplete
+
+
+class ArrowSeriesCatNamespace(ArrowSeriesNamespace):
+    def get_categories(self) -> ArrowSeries:
+        # NOTE: Should be `list[pa.DictionaryArray]`, but `DictionaryArray` has no attributes
+        chunks: Incomplete = self.native.chunks
+        return self.with_native(pa.concat_arrays(x.dictionary for x in chunks).unique())