CLN: doc string (pandas-dev#23469)

Author: topper-123

pandas/core/generic.py

@@ -5279,7 +5279,9 @@ def astype(self, dtype, copy=True, errors='raise', **kwargs):
 
         Convert to ordered categorical type with custom ordering:
 
-        >>> ser.astype('category', ordered=True, categories=[2, 1])
+        >>> cat_dtype = pd.api.types.CategoricalDtype(
+        ...                     categories=[2, 1], ordered=True)
+        >>> ser.astype(cat_dtype)
         0    1
         1    2
         dtype: category