code: def complete_shells(line, text, predicate=lambda i: True):
      
      res = [i.display_name + ' ' for i in dispatchers.all_instances() if
             i.display_name.startswith(text) and
             predicate(i) and
             ' ' + i.display_name + ' ' not in line]
      return res
docs: Return the shell names to include in the completion