code: def format_usage(self, usage=None):
          
          if usage is None:
              usage = self.docs['usage']
          if usage is not None:
              return usage[0] % self.docvars
          usage = self.docvars['command']
          if self.basic_option_names.get('help'):
              usage += ' [--%s]' % self.basic_option_names.get('help')
          if self.options:
              usage += ' <OPTIONS>'
          optional = 0
          for posarg in self.positional_args:
              usage += ' '
              if posarg.optional:
                  usage += "[" 
                  optional += 1
              usage += posarg.displayname
              if posarg.recurring:
                  usage += ' [%s2 [...]]' % posarg.displayname
          usage += ']' * optional
          return usage
docs: Return a formatted usage string. 
          
          If usage is None, use self.docs['usage'], and if that is also None, 
          generate one.