bpo-31942: Document optional support of start and stop attributes in Sequence.index method (#4277)
diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index e89e84b..a5c7bfc 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -899,6 +899,9 @@
def index(self, value, start=0, stop=None):
'''S.index(value, [start, [stop]]) -> integer -- return first index of value.
Raises ValueError if the value is not present.
+
+ Supporting start and stop arguments is optional, but
+ recommended.
'''
if start is not None and start < 0:
start = max(len(self) + start, 0)