def prepare_headers(self, headers, cache_info=None):
if self.use_advanced and cache_info:<EOL><INDENT>hkeys = headers.keys()<EOL>if cache_info.access_time and "<STR_LIT>" not in hkeys:<EOL><INDENT>headers['<STR_LIT>'] = cache_info.access_time.strftime(<EOL>"<STR_LIT>"<EOL>)<EOL><DEDENT>if cache_info.etag and "<STR_LIT>" not in hkeys:<EOL><INDENT>headers['<STR_LIT>'] = cache_info.etag<EOL><DEDENT><DEDENT>return headers<EOL>
Prepare headers object for request (add cache information

:param headers: Headers object
:type headers: dict
:param cache_info: Cache information to add
:type cache_info: floscraper.models.CacheInfo
:return: Prepared headers
:rtype: dict