user_options

ExtrasCommand.user_options = [('save=', 'o', 'Output extras in requirements.txt format to this file'), ('extra=', 'e', 'List requirements for this specific extra name, e.g. --extra=cache'), ('list', 'l', 'Only list extra names, not the requirements they include'), ('install', 'i', 'Install all extras requirements, or if --extra/-e is specified, only that extra.')]