code: def _ValidateCacheFileMetadataHeader(self, cache_file_metadata_header):
      
      # TODO: add support for format version 2 and 3
      return (
          cache_file_metadata_header.key_size > 0 and
          cache_file_metadata_header.key_size < self._MAXIMUM_URL_LENGTH and
          cache_file_metadata_header.format_version == 1 and
          cache_file_metadata_header.last_fetched_time > 0 and
          cache_file_metadata_header.fetch_count > 0)
docs: Determines whether the cache file metadata header is valid.
  
      Args:
        cache_file_metadata_header (firefox_cache2_file_metadata_header): cache
            file metadata header.
  
      Returns:
        bool: True if the cache file metadata header is valid.