code: def p_opt_order(self, p):
          '''opt_order :
                       | ORDER LPAREN IDENTIFIER RPAREN'''
          if len(p) > 1:
              if p[3] not in 'CF':
                  raise PythranSyntaxError("Invalid Pythran spec. "
                                           "Unknown order '{}'".format(p[3]))
              p[0] = p[3]
          else:
              p[0] = Nonf p_opt_order(self, p):
          '''opt_order :
                       | ORDER LPAREN IDENTIFIER RPAREN'''
          if len(p) > 1:
              if p[3] not in 'CF':
                  raise PythranSyntaxError("Invalid Pythran spec. "
                                           "Unknown order '{}'".format(p[3]))
              p[0] = p[3]
          else:
              p[0] = None
docs: opt_order :
                       | ORDER LPAREN IDENTIFIER RPAREN