class_docstr: Non-blocking HTTP client with no external dependencies.
  
  This class implements an HTTP 1.1 client on top of Tornado's IOStreams.
  Some features found in the curl-based AsyncHTTPClient are not yet
  supported.  In particular, proxies are not supported, connections
  are not reused, and callers cannot select the network interface to be
  used.
class_docstr_tok: ["Non-blocking","HTTP","client","with","no","external","dependencies",".","This","class","implements","an","HTTP","1.1","client","on","top","of","Tornado","'s","IOStreams",".","Some","features","found","in","the","curl-based","AsyncHTTPClient","are","not","yet","supported",".","In","particular",",","proxies","are","not","supported",",","connections","are","not","reused",",","and","callers","can","not","select","the","network","interface","to","be","used","."]
code: def _release_fetch(self, key):
      del self.active[key]
      self._process_queue()
  
imports: from __future__ import absolute_import, division, print_function
  from tornado.escape import utf8, _unicode
  from tornado import gen
  from tornado.httpclient import HTTPResponse, HTTPError, AsyncHTTPClient, main, _RequestProxy
  from tornado import httputil
  from tornado.http1connection import HTTP1Connection, HTTP1ConnectionParameters
  from tornado.iostream import StreamClosedError
  from tornado.netutil import Resolver, OverrideResolver, _client_ssl_defaults
  from tornado.log import gen_log
  from tornado import stack_context
  from tornado.tcpclient import TCPClient
  from tornado.util import PY3
  import base64
  import collections
  import copy
  import functools
  import re
  import socket
  import sys
  from io import BytesIO
label_desc: Use image node_id 7 for calling the SimpleAsyncHTTPClient obj's underlying member method code with example usage: obj._release_fetch(key) without return types