code: def common(self):
          
          res = {"kty": self.kty}
          if self.use:
              res["use"] = self.use
          if self.kid:
              res["kid"] = self.kid
          if self.alg:
              res["alg"] = self.alg
          return res
docs: Return the set of parameters that are common to all types of keys.
  
          :return: Dictionary