DOC: Added a Multi Index example for the Series.sum method (pandas-dev#23279)

Author: vadakattu

pandas/core/generic.py

@@ -10185,6 +10185,40 @@ def _doc_parms(cls):
 _sum_examples = """\
 Examples
 --------
+``MultiIndex`` series example of monthly rainfall
+
+>>> index = pd.MultiIndex.from_product(
+...     [['London', 'New York'], ['Jun', 'Jul', 'Aug']],
+...     names=['city', 'month'])
+>>> s = pd.Series([47, 35, 54, 112, 117, 113], index=index)
+>>> s
+city      month
+London    Jun       47
+          Jul       35
+          Aug       54
+New York  Jun      112
+          Jul      117
+          Aug      113
+dtype: int64
+
+>>> s.sum()
+478
+
+Sum using level names, as well as indices
+
+>>> s.sum(level='city')
+city
+London      136
+New York    342
+dtype: int64
+
+>>> s.sum(level=1)
+month
+Jun    159
+Jul    152
+Aug    167
+dtype: int64
+
 By default, the sum of an empty or all-NA Series is ``0``.
 
 >>> pd.Series([]).sum()  # min_count=0 is the default