code: def format(self, format_spec='f'):
          u
          if format_spec == '' or format_spec == 'f':
              cpf = CPF.clean(self._cpf)
              return '{0}.{1}.{2}-{3}'.format(cpf[0:3], cpf[3:6], cpf[6:9], cpf[9:11])
          if format_spec == 'r':
              return self._cpf
          raise ValueError(
              "Unknown format code '{0}' for object of type '{1}'".format(format_spec, CPF.__name__))
docs: u"""
          Formata o CPF.
  
          Códigos de formatação:
          r -> raw
          f -> formatado
  
          >>> cpf = CPF(58119443659)
          >>> cpf.format('r')
          '58119443659'
          >>> cpf.format('f')
          '581.194.436-59'