code: def revoke_access_token(credential):
      
      url = build_url(auth.SERVER_HOST, auth.REVOKE_PATH)
  
      args = {
          'token': credential.access_token,
      }
  
      response = post(url=url, params=args)
  
      if response.status_code == codes.ok:
          return
  
      message = 'Failed to revoke access token: {}.'
      message = message.format(response.reason)
      raise ClientError(response, message)
docs: Revoke an access token.
      All future requests with the access token will be invalid.
      Parameters
          credential (OAuth2Credential)
              An authorized user's OAuth 2.0 credentials.
      Raises
          ClientError (APIError)
              Thrown if there was an HTTP error.