[Fab-user] how to use prompts ?

[Song]

I am using Fabric 1.10.2  I  am trying to control an interactive prompt referred to http://docs.fabfile.org/en/latest/usage/env.html#prompts , but it is unclear about describing how to use prompts in conjunction with the run() method. 

def pt5():
    #with settings(prompts={'Do you want to continue [Y/n]? ': 'Y'}):
     env.prompts={'Do you want to continue [Y/n]? ': 'Y'}
     with settings(prompts=(env.prompts)):
      run('apt-get update')
      run('apt-get upgrade')

or 

def pt5():
     with settings(prompts={'Do you want to continue [Y/n]? ': 'Y'}):
     #env.prompts={'Do you want to continue [Y/n]? ': 'Y'}
     #with settings(prompts=(env.prompts)):
       run('apt-get update')
       run('apt-get upgrade')


But both prompts were  not working at all, Anybody know how to use prompts{} ?

Thanks in advance .

GM