Write runs(s) returning [[char, count], …] for consecutive runs using itertools.groupby.
runs(s)
[[char, count], …]
itertools.groupby
runs('aaabbc') → [['a', 3], ['b', 2], ['c', 1]]
runs('') → []
Submit runs 4 tests, including hidden edge cases.
Run your code to see the output here.