diff --git a/native-datatypes.html b/native-datatypes.html
index 07a773b..e3c755c 100644
--- a/native-datatypes.html
+++ b/native-datatypes.html
@@ -505,15 +505,18 @@ KeyError: 'db.diveintopython3.org'
... 1024: ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']}
>>> len(SUFFIXES) ①
2
->>> SUFFIXES[1000] ②
+>>> 1000 in SUFFIXES ②
+True
+>>> SUFFIXES[1000] ③
['KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']
->>> SUFFIXES[1024] ③
+>>> SUFFIXES[1024] ④
['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']
->>> SUFFIXES[1000][3] ④
+>>> SUFFIXES[1000][3] ⑤
'TB'
-- As with lists, the
len() function gives you the number of items in a dictionary.
- 1000 is a key in the SUFFIXES dictionary; its value is a list of eight items (eight strings, to be precise).
+- Like lists and sets [FIXME-xref], the
len() function gives you the number of keys in a dictionary.
+ - And like lists and sets, you can use the
in operator to test whether a specific key is defined in a dictionary.
+ 1000 is a key in the SUFFIXES dictionary; its value is a list of eight items (eight strings, to be precise).
- Similarly,
1024 is a key in the SUFFIXES dictionary; its value is also a list of eight items.
- Since
SUFFIXES[1000] is a list, you can address individual items in the list by their 0-based index.