class Pry::Command::ChangePrompt

def change_prompt(prompt)
  if Pry::Prompt[prompt]
    pry_instance.prompt = Pry::Prompt[prompt]
  else
    raise Pry::CommandError,
          "'#{prompt}' isn't a known prompt. Run `change-prompt --list` " \
          "to see the list of known prompts."
  end
end