old_contents: from typing import Dict, cast
  import json
  import re
  
  from bs4 import BeautifulSoup as Soup
  
  from .constants import WATCH_LATER_URL
  from .typing.ytcfg import YtcfgDict
  from .util import first
  
  
  def find_ytcfg(soup: Soup) -> YtcfgDict:
      return cast(
          YtcfgDict,
          first(json.JSONDecoder().raw_decode(
              re.sub(
                  r'.+ytcfg.set\(\{', '{',
                  first(x for x in soup.select('script')
                        if '"INNERTUBE_CONTEXT_CLIENT_VERSION":' in
                        x.text).text.strip().replace('\n', ''), 1))))
  
  
  def ytcfg_headers(ytcfg: YtcfgDict) -> Dict[str, str]:
      return {
          'x-spf-previous': WATCH_LATER_URL,
          'x-spf-referer': WATCH_LATER_URL,
          'x-youtube-client-name': str(ytcfg['INNERTUBE_CONTEXT_CLIENT_NAME']),
          'x-youtube-client-version': ytcfg['INNERTUBE_CONTEXT_CLIENT_VERSION'],
          'x-youtube-identity-token': ytcfg['ID_TOKEN'],
          'x-youtube-page-cl': str(ytcfg['PAGE_CL']),
          'x-youtube-utc-offset': '-240',
          'x-youtube-variants-checksum': ytcfg['VARIANTS_CHECKSUM'],
      }
  
new_contents: from typing import Dict, cast
  import json
  import re
  
  from bs4 import BeautifulSoup as Soup
  
  from .constants import WATCH_LATER_URL
  from .typing.ytcfg import YtcfgDict
  from .util import first
  
  
  def find_ytcfg(soup: Soup) -> YtcfgDict:
      return cast(
          YtcfgDict,
          first(json.JSONDecoder().raw_decode(
              re.sub(
                  r'.+ytcfg.set\(\{', '{',
                  first(x for x in soup.select('script')
                        if '"INNERTUBE_CONTEXT_CLIENT_VERSION":' in
                        x.text).text.strip().replace('\n', ''), 1))))
  
  
  def ytcfg_headers(ytcfg: YtcfgDict) -> Dict[str, str]:
      return {
          'x-spf-previous': WATCH_LATER_URL,
          'x-spf-referer': WATCH_LATER_URL,
          'x-youtube-client-name': str(ytcfg['INNERTUBE_CONTEXT_CLIENT_NAME']),
          'x-youtube-client-version': ytcfg['INNERTUBE_CONTEXT_CLIENT_VERSION'],
          'x-youtube-identity-token': ytcfg['ID_TOKEN'],
          'x-youtube-page-cl': str(ytcfg['PAGE_CL']),
          'x-youtube-utc-offset': '-240',
      }
  
subject: remove non-existent key