How to slice / rebin a categorical axis?

[kondratyevd]

1. What is the proper way to get a slice that includes multiple bins of a StrCategory axis?
   I tried a few intuitive ways (see below), but they don't seem to work.

from hist import Hist
import boost_histogram as bh

h = Hist.new.StrCat(['A', 'B', 'C']).Double()

subset = ['A','B']

h['A'] # ok
h[['A']] # ok
h[subset]  # error: wrong number of indices for histogram
h[[subset]]  # error: must be a slice, an integer, or follow the locator protocol
h[bh.loc(subset)]  # error: only integer scalar arrays can be converted to a scalar index

2. Follow-up question: is it possible to rebin categorical axes (i.e. merge categories)?
   Something along the lines with:

# input:
Hist(StrCategory(['A', 'B', 'C']), storage=Double())

rebin_scheme = {
    'AB': ['A', 'B'],
    'C': ['C']
}

# do something

# output:
Hist(StrCategory(['AB', 'C']), storage=Double())

[kondratyevd]

Selection lists are available in v2.4.0 (#259), which solves my issue. In the example above, h[subset] works in v2.4.0.
Thanks @henryiii !