code: def check_etag_header(self) -> bool:
          
          computed_etag = utf8(self._headers.get("Etag", ""))
          # Find all weak and strong etag values from If-None-Match header
          # because RFC 7232 allows multiple etag values in a single header.
          etags = re.findall(
              br'\*|(?:W/)?"[^"]*"', utf8(self.request.headers.get("If-None-Match", ""))
          )
          if not computed_etag or not etags:
              return False
  
          match = False
          if etags[0] == b"*":
              match = True
          else:
              # Use a weak comparison when comparing entity-tags.
              def val(x: bytes) -> bytes:
                  return x[2:] if x.startswith(b"W/") else x
  
              for etag in etags:
                  if val(etag) == val(computed_etag):
                      match = True
                      break
          return match
docs: Checks the ``Etag`` header against requests's ``If-None-Match``.
  
          Returns ``True`` if the request's Etag matches and a 304 should be
          returned. For example::
  
              self.set_etag_header()
              if self.check_etag_header():
                  self.set_status(304)
                  return
  
          This method is called automatically when the request is finished,
          but may be called earlier for applications that override
          `compute_etag` and want to do an early check for ``If-None-Match``
          before completing the request.  The ``Etag`` header should be set
          (perhaps with `set_etag_header`) before calling this method.