class_docstr: Abstract implementation of OAuth 2.0.
  
  See `FacebookGraphMixin` or `GoogleOAuth2Mixin` below for example
  implementations.
  
  Class attributes:
  
  * ``_OAUTH_AUTHORIZE_URL``: The service's authorization url.
  * ``_OAUTH_ACCESS_TOKEN_URL``:  The service's access token url.
class_docstr_tok: ["Abstract","implementation","of","OAuth","2.0",".","See","`","FacebookGraphMixin","`","or","`","GoogleOAuth2Mixin","`","below","for","example","implementations",".","Class","attributes",":","*","``","_OAUTH_AUTHORIZE_URL","``",":","The","service","'s","authorization","url",".","*","``","_OAUTH_ACCESS_TOKEN_URL","``",":","The","service","'s","access","token","url","."]
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.
  
  .. versionadded:: 4.3
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",".","..","versionadded",":",":","4.3"]
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.
  
      .. versionadded:: 4.3
      """
      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 3 for calling the OAuth2Mixin obj's underlying member method code with example usage: obj.get_auth_http_client() and returns: httpclient