code: def regenerate_signing_key(self, secret_key=None, region=None,
                                 service=None, date=None):
          
          if secret_key is None and (self.signing_key is None or
                                     self.signing_key.secret_key is None):
              raise NoSecretKeyError
  
          secret_key = secret_key or self.signing_key.secret_key
          region = region or self.region
          service = service or self.service
          date = date or self.date
          if self.signing_key is None:
              store_secret_key = True
          else:
              store_secret_key = self.signing_key.store_secret_key
  
          self.signing_key = AWS4SigningKey(secret_key, region, service, date,
                                            store_secret_key)
  
          self.region = region
          self.service = service
          self.date = self.signing_key.date
docs: Regenerate the signing key for this instance. Store the new key in
          signing_key property.
  
          Take scope elements of the new key from the equivalent properties
          (region, service, date) of the current AWS4Auth instance. Scope
          elements can be overridden for the new key by supplying arguments to
          this function. If overrides are supplied update the current AWS4Auth
          instance's equivalent properties to match the new values.
  
          If secret_key is not specified use the value of the secret_key property
          of the current AWS4Auth instance's signing key. If the existing signing
          key is not storing its secret key (i.e. store_secret_key was set to
          False at instantiation) then raise a NoSecretKeyError and do not
          regenerate the key. In order to regenerate a key which is not storing
          its secret key, secret_key must be supplied to this function.
  
          Use the value of the existing key's store_secret_key property when
          generating the new key. If there is no existing key, then default
          to setting store_secret_key to True for new key.