DOC: Updated aggregate docstring

pandas/core/generic.py

@@ -5076,6 +5076,9 @@ def pipe(self, func, *args, **kwargs):
         -----
         `agg` is an alias for `aggregate`. Use the alias.
 
+        Pandas operations generally exclude NaNs. For example, `agg(np.nanmedian)`,
+        `agg(np.median)`, and `agg('median')` will return the same result.
+
         A passed user-defined-function will be passed a Series for evaluation.
         {examples}"""
     )