class Net::IMAP

def sort_internal(cmd, sort_keys, search_keys, charset)
  if search_keys.instance_of?(String)
    search_keys = [RawData.new(search_keys)]
  else
    normalize_searching_criteria(search_keys)
  end
  normalize_searching_criteria(search_keys)
  synchronize do
    send_command(cmd, sort_keys, charset, *search_keys)
    clear_responses("SORT").last || []
  end
end