def sort(sort_keys, search_keys, charset)
      return sort_internal("SORT", sort_keys, search_keys, charset)
    end
Sends a SORT command to sort messages in the mailbox.
Returns an array of message sequence numbers. For example:

p imap.sort(["FROM"], ["ALL"], "US-ASCII")
#=> [1, 2, 3, 5, 6, 7, 8, 4, 9]
p imap.sort(["DATE"], ["SUBJECT", "hello"], "US-ASCII")
#=> [6, 7, 8, 1]

See [SORT-THREAD-EXT] for more details.