itertools doc: examples for groupby() and tee() (python#120618)

Author: ferdnyc

Doc/library/itertools.rst

@@ -58,12 +58,12 @@ Iterator                        Arguments                       Results
 :func:`compress`                data, selectors                 (d[0] if s[0]), (d[1] if s[1]), ...                 ``compress('ABCDEF', [1,0,1,0,1,1]) → A C E F``
 :func:`dropwhile`               predicate, seq                  seq[n], seq[n+1], starting when predicate fails     ``dropwhile(lambda x: x<5, [1,4,6,3,8]) → 6 3 8``
 :func:`filterfalse`             predicate, seq                  elements of seq where predicate(elem) fails         ``filterfalse(lambda x: x<5, [1,4,6,3,8]) → 6 8``
-:func:`groupby`                 iterable[, key]                 sub-iterators grouped by value of key(v)
+:func:`groupby`                 iterable[, key]                 sub-iterators grouped by value of key(v)            ``groupby(['A','B','ABC'], len) → (1, A B) (3, ABC)``
 :func:`islice`                  seq, [start,] stop [, step]     elements from seq[start:stop:step]                  ``islice('ABCDEFG', 2, None) → C D E F G``
 :func:`pairwise`                iterable                        (p[0], p[1]), (p[1], p[2])                          ``pairwise('ABCDEFG') → AB BC CD DE EF FG``
 :func:`starmap`                 func, seq                       func(\*seq[0]), func(\*seq[1]), ...                 ``starmap(pow, [(2,5), (3,2), (10,3)]) → 32 9 1000``
 :func:`takewhile`               predicate, seq                  seq[0], seq[1], until predicate fails               ``takewhile(lambda x: x<5, [1,4,6,3,8]) → 1 4``
-:func:`tee`                     it, n                           it1, it2, ... itn  splits one iterator into n
+:func:`tee`                     it, n                           it1, it2, ... itn  splits one iterator into n       ``tee('ABC', 2) → A B C, A B C``
 :func:`zip_longest`             p, q, ...                       (p[0], q[0]), (p[1], q[1]), ...                     ``zip_longest('ABCD', 'xy', fillvalue='-') → Ax By C- D-``
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