code: def execute(helper, config, args):
      
      old_env_name = args.old_environment
      new_env_name = args.new_environment
  
      # swap C-Names
      out("Assuming that {} is the currently active environment...".format(old_env_name))
      out("Swapping environment cnames: {} will become active, {} will become inactive.".format(new_env_name,
                                                                                                old_env_name))
      helper.swap_environment_cnames(old_env_name, new_env_name)
      helper.wait_for_environments([old_env_name, new_env_name], status='Ready', include_deleted=False)
docs: Swaps old and new URLs.
      If old_environment was active, new_environment will become the active environment