GH36602 (#43620)

DOC

Co-authored-by: kendall smith <[email protected]>

Author: kasmith11

pandas/core/groupby/groupby.py

@@ -173,6 +173,10 @@ class providing the base-class of operations.
         The resulting dtype will reflect the return value of the passed ``func``,
         see the examples below.
 
+    Functions that mutate the passed object can produce unexpected
+    behavior or errors and are not supported. See :ref:`gotchas.udf-mutation`
+    for more details.
+
     Examples
     --------
     {examples}