Open
Description
As hinted in #361 and a follow-up to #634, it would often be useful to support group keys in set_labels:
>>> arr = ndtest(10)
>>> arr
a a0 a1 a2 a3 a4 a5 a6 a7 a8 a9
0 1 2 3 4 5 6 7 8 9
>>> arr.set_labels({'a1,a3,a4': 'a134', 'a6,a8': 'a68'})
a a0 a134 a2 a134 a134 a5 a68 a7 a68 a9
0 1 2 3 4 5 6 7 8 9
>>> arr = ndtest("a=01..10").with_total()
>>> arr
a 01 02 03 04 05 06 07 08 09 10 total
0 1 2 3 4 5 6 7 8 9 45
>>> arr.set_labels({'01..10': int})
a 1 2 3 4 5 6 7 8 9 10 total
0 1 2 3 4 5 6 7 8 9 45