code: def read(self, prompt='', clean=lambda x: x):
          
          ans = read(prompt + ' ')
          return clean(ans)
docs: Display a prompt and ask user for input
  
          A function to clean the user input can be passed as ``clean`` argument.
          This function takes a single value, which is the string user entered,
          and returns a cleaned value. Default is a pass-through function, which
          is an equivalent of::
  
              def clean(val):
                  return val