code: def parse_etag_header(header):
      
      m = etag_header_re.match(header.strip())
      if not m:
          return []
      if m.group(1):  # star
          return m.group(1)
      else:  # list of entity tags
          return etag_re.findall(header)
docs: Parse a header containing one or more ETags or a wildcard ('*').
  
      Returns the string '*' or a list of ETags as (weak, etag) tuples.
      `weak` is the prefix designating a weak ETag, or the empty string.
      `etag` is the ETag (including quotes) with the weak prefix stripped
      off. Returns an empty list if the header could not be parsed.
  
      Example:
  
      >>> parse_etag_header('*')
      '*'
      >>> parse_etag_header('"foo"  ')
      [('', '"foo"')]
      >>> parse_etag_header('"foo", w/"bar", W/"baz"')
      [('', '"foo"'), ('w/', '"bar"'), ('W/', '"baz"')]
      >>> parse_etag_header('invalid')
      []