to_array_object: type dtype as str, note possibilities (#213)

* use str in to_array_object

* keep dtype, but document accepted types

* remove namespace

* Fix a typo

---------

Co-authored-by: Ralf Gommers <ralf.gommers@gmail.com>

Author: MarcoGorelli

spec/API_specification/dataframe_api/column_object.py

@@ -695,8 +695,21 @@ def to_array_object(self, dtype: Any) -> Any:
 
         Parameters
         ----------
-        dtype : Any
+        dtype : DType
             The dtype of the array-API-compliant object to return.
+            Must be one of:
+
+            - Bool()
+            - Int8()
+            - Int16()
+            - Int32()
+            - Int64()
+            - UInt8()
+            - UInt16()
+            - UInt32()
+            - UInt64()
+            - Float32()
+            - Float64()
         
         Returns
         -------

spec/API_specification/dataframe_api/dataframe_object.py

@@ -823,8 +823,21 @@ def to_array_object(self, dtype: Any) -> Any:
 
         Parameters
         ----------
-        dtype : Any
+        dtype : DType
             The dtype of the array-API-compliant object to return.
+            Must be one of:
+
+            - Bool()
+            - Int8()
+            - Int16()
+            - Int32()
+            - Int64()
+            - UInt8()
+            - UInt16()
+            - UInt32()
+            - UInt64()
+            - Float32()
+            - Float64()
         
         Returns
         -------