code: def headers(self):
          
          if py3k:
              return dict((k.lower(), v) for k, v in self.getheaders())
          else:
              return dict(self.getheaders())
docs: Response headers.
  
          Response headers is a dict with all keys in lower case.
  
          >>> import urlfetch
          >>> response = urlfetch.get("http://docs.python.org/")
          >>> response.headers
          {
              'content-length': '8719',
              'x-cache': 'MISS from localhost',
              'accept-ranges': 'bytes',
              'vary': 'Accept-Encoding',
              'server': 'Apache/2.2.16 (Debian)',
              'last-modified': 'Tue, 26 Jun 2012 19:23:18 GMT',
              'connection': 'close',
              'etag': '"13cc5e4-220f-4c36507ded580"',
              'date': 'Wed, 27 Jun 2012 06:50:30 GMT',
              'content-type': 'text/html',
              'x-cache-lookup': 'MISS from localhost:8080'
          }