docs: def help_text(cls):
          """Return a slack-formatted list of commands with their usage."""
          docs = [cmd_func.__doc__ for cmd_func in cls.commands.values()]
  
          # Don't want to include 'usage: ' or explanation.
          usage_lines = [doc.partition('\n')[0] for doc in docs]
          terse_lines = [line[len('Usage: '):] for line in usage_lines]
          terse_lines.sort()
          return '\n'.join(['Available commands:\n'] + terse_lines)