docs: def format_cli(self, value):
          """
          Build a single parameter argument.
  
          :return: list of CLI strings -- not escaped. If the parameter should not be expressed, returns None.
          :rtype: list[str]|None
          """
          if value is None or (self.type == 'flag' and not value):
              return None
          pass_as_bits = text_type(self.pass_as or self.default_pass_as).split()
          env = dict(name=self.name, value=value, v=value)
          return [bit.format(**env) for bit in pass_as_bits]