code: def p_route_version(self, p):
          
          if len(p) > 2:
              if p[2] <= 0:
                  msg = "Version number should be a positive integer."
                  self.errors.append((msg, p.lineno(2), self.path))
              p[0] = p[2]
          else:
              p[0] = 1
docs: route_version : COLON INTEGER
                           | empty