class_docstr: Base class for html_form and http_auth authenticators
      
class_docstr_tok: ["Base","class","for","html_form","and","http_auth","authenticators"]
code: def authenticate(self, url, credential, session, update=False):
      # we should use specified URL for this authentication first
      lgr.info("http session: Authenticating into session for %s", url)
      post_url = self.url if self.url else url
      credential.set_context(auth_url=post_url)
      credentials = credential()
  
      # The whole thing relies on server first spitting out 401
      # and client getting again with 'Authentication:' header
      # So we need custom handling for those, while keeping track not
      # of cookies per se, but of 'Authentication:' header which is
      # to be used in subsequent GETs
      response = self._post_credential(credentials, post_url, session)
      if response is None:
          # authentication did not involve any interaction, nothing to
          # check at this point
          return
  
      # Handle responses if there was initial authentication exchange,
      # e.g. posting to a form and getting a cookie etc
      err_prefix = "Authentication to %s failed: " % post_url
      try:
          check_response_status(response, err_prefix, session=session)
      except DownloadError:
          # It might have happened that the return code was 'incorrect'
          # and we did get some feedback, which we could analyze to
          # figure out actual problem.  E.g. in case of nersc of crcns
          # it returns 404 (not found) with text in the html
          if response is not None and response.text:
              self.check_for_auth_failure(response.text, err_prefix)
          raise
  
      response_text = response.text
      self.check_for_auth_failure(response_text, err_prefix)
  
      if self.success_re:
          # the one which must be used to verify success
          # verify that we actually logged in
          for success_re in self.success_re:
              if not re.search(success_re, response_text):
                  raise AccessDeniedError(
                      err_prefix
                      + " returned output did not match 'success' regular expression %s"
                      % success_re
                  )
  
      cookies_dict = {}
      if response.cookies:
          cookies_dict = requests.utils.dict_from_cookiejar(
              response.cookies
          )
      if self.session_cookies:
          # any session cookies to store
          cookies_dict.update(
              {k: session.cookies[k] for k in self.session_cookies}
          )
  
      if cookies_dict:
          if (url in cookies_db) and update:
              cookies_db[url].update(cookies_dict)
          else:
              cookies_db[url] = cookies_dict
          # assign cookies for this session
          for c, v in cookies_dict.items():
              if c not in session.cookies or session.cookies[c] != v:
                  session.cookies[c] = v  # .update(cookies_dict)
  
      return response
  
imports: import re
  import requests
  import requests.auth
  from requests.utils import parse_dict_header
  import io
  from time import sleep
  from ..None import __version__
  from ..utils import ensure_list_from_str, ensure_dict_from_str, ensure_bytes
  from ..dochelpers import borrowkwargs
  from ..ui import ui
  from ..utils import auto_repr
  from ..support.network import get_url_filename
  from ..support.network import get_response_disposition_filename
  from ..support.network import rfc2822_to_epoch
  from ..support.cookies import cookies_db
  from ..support.status import FileStatus
  from ..support.exceptions import AccessDeniedError, AccessFailedError, CapturedException, DownloadError, UnhandledRedirectError
  from .base import Authenticator
  from .base import BaseDownloader, DownloaderSession
  from logging import getLogger
  from ..log import LoggerHelper
label_desc: Use image node_id 2 for calling the HTTPBaseAuthenticator obj's underlying member method code with example usage: obj.authenticate(url, credential, session, update) and returns: response