class_docstr: Abstract implementation of OpenID and Attribute Exchange.
  
  Class attributes:
  
  * ``_OPENID_ENDPOINT``: the identity provider's URI.
class_docstr_tok: ["Abstract","implementation","of","OpenID","and","Attribute","Exchange",".","Class","attributes",":","*","``","_OPENID_ENDPOINT","``",":","the","identity","provider","'s","URI","."]
docstr: Returns the `.AsyncHTTPClient` instance to be used for auth requests.
  
  May be overridden by subclasses to use an HTTP client other than
  the default.
docstr_tok: ["Returns","the","`",".AsyncHTTPClient","`","instance","to","be","used","for","auth","requests",".","May","be","overridden","by","subclasses","to","use","an","HTTP","client","other","than","the","default","."]
code: def get_auth_http_client(self) -> httpclient.AsyncHTTPClient:
      """Returns the `.AsyncHTTPClient` instance to be used for auth requests.
  
      May be overridden by subclasses to use an HTTP client other than
      the default.
      """
      return httpclient.AsyncHTTPClient()
  
imports: import base64
  import binascii
  import hashlib
  import hmac
  import time
  import urllib.parse
  import uuid
  import warnings
  from tornado import httpclient
  from tornado import escape
  from tornado.httputil import url_concat
  from tornado.util import unicode_type
  from tornado.web import RequestHandler
  from typing import List, Any, Dict, cast, Iterable, Union, Optional
label_desc: Use image node_id 4 for calling the OpenIdMixin obj's underlying member method code with example usage: obj.get_auth_http_client() and returns: httpclient