How to use the wsgiref.util.is_hop_by_hop function in wsgiref

def testHopByHop(self):
        for hop in (
            "Connection Keep-Alive Proxy-Authenticate Proxy-Authorization "
            "TE Trailers Transfer-Encoding Upgrade"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.failUnless(util.is_hop_by_hop(alt))

        # Not comprehensive, just a few random header names
        for hop in (
            "Accept Cache-Control Date Pragma Trailer Via Warning"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.failIf(util.is_hop_by_hop(alt))

def testHopByHop(self):
        for hop in (
            "Connection Keep-Alive Proxy-Authenticate Proxy-Authorization "
            "TE Trailers Transfer-Encoding Upgrade"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.assertTrue(util.is_hop_by_hop(alt))

        # Not comprehensive, just a few random header names
        for hop in (
            "Accept Cache-Control Date Pragma Trailer Via Warning"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.assertFalse(util.is_hop_by_hop(alt))

def testHopByHop(self):
        for hop in (
            "Connection Keep-Alive Proxy-Authenticate Proxy-Authorization "
            "TE Trailers Transfer-Encoding Upgrade"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.assertTrue(util.is_hop_by_hop(alt))

        # Not comprehensive, just a few random header names
        for hop in (
            "Accept Cache-Control Date Pragma Trailer Via Warning"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.assertFalse(util.is_hop_by_hop(alt))

def testHopByHop(self):
        for hop in (
            "Connection Keep-Alive Proxy-Authenticate Proxy-Authorization "
            "TE Trailers Transfer-Encoding Upgrade"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.failUnless(util.is_hop_by_hop(alt))

        # Not comprehensive, just a few random header names
        for hop in (
            "Accept Cache-Control Date Pragma Trailer Via Warning"
        ).split():
            for alt in hop, hop.title(), hop.upper(), hop.lower():
                self.failIf(util.is_hop_by_hop(alt))

else:
                raise ValueError("Unknown request type %s." % req_spec['type'])

            http_params = bottle.request.query_string
            http_body = bottle.request.body.read()
            http_method = resp_spec.get('method') or bottle.request.method or 'GET'
            http_timeout = req_spec.get('timeout') or DEFAULT_TIMEOUT
            http_headers = {k.lower(): v for k, v in\
                            util.filter_request_headers(bottle.request, allow_host=self.allow_host).items()}
            http_headers.update(req_spec.get('headers') or {})
            sess = session_pool.get_session()
            resp_obj = sess.request(http_method, url, params=http_params, data=http_body,
                                    headers=http_headers, timeout=http_timeout, allow_redirects=False)
            ret['body'] = resp_obj.content
            for k, v in resp_obj.headers.items():
                if (not is_hop_by_hop(k)) and not k.lower() in ['content-length']:
                    ret['headers'][k.lower()] = v
            if ret['headers'].get('location'):
                ret['headers']['location'] = util.replace_location_host(ret['headers']['location'],
                                                                        url, bottle.request.urlparts.netloc)
 
            set_cookie = ret['headers'].pop('set-cookie', None)
            if set_cookie:
                ret['headers']['set-cookie'] =\
                        set([i.strip() for i in re.split(r",(?![^=]+;)", set_cookie) if i.strip()])
            ret['status'] = resp_obj.status_code
        elif resp_type in handlers.HANDLERS:
            handler_object = handlers.get_handler_object(req_spec, resp_spec,
                                                         root_prefix=self.prefix)
            pos = suffix.find(req_spec['path'])
            ret = handler_object.dispatch(suffix[pos + len(req_spec['path']): ])
        else:

"SERVER_PROTOCOL": "HTTP/{}.{}".format(*request.version),
            "wsgi.version": (1, 0),
            "wsgi.url_scheme": url_scheme,
            "wsgi.input": body,
            "wsgi.errors": self._stderr,
            "wsgi.multithread": True,
            "wsgi.multiprocess": False,
            "wsgi.run_once": False,
            "asyncio.loop": self._loop,
            "asyncio.executor": self._executor,
            "aiohttp.request": request,
        }
        # Add in additional HTTP headers.
        for header_name in request.headers:
            header_name = header_name.upper()
            if not(is_hop_by_hop(header_name)) and header_name not in ("CONTENT-LENGTH", "CONTENT-TYPE"):
                header_value = ",".join(request.headers.getall(header_name))
                environ["HTTP_" + header_name.replace("-", "_")] = header_value
        # All done!
        return environ

if not _HTTP_TOKEN_RE.match(name):
        raise appinfo_errors.InvalidHttpHeaderName(
            'An HTTP header must be a non-empty RFC 2616 token.')


      if name in _HTTP_REQUEST_HEADERS:
        raise appinfo_errors.InvalidHttpHeaderName(
            '%r can only be used in HTTP requests, not responses.'
            % original_name)


      if name.startswith('x-appengine'):
        raise appinfo_errors.InvalidHttpHeaderName(
            'HTTP header names that begin with X-Appengine are reserved.')

      if wsgiref.util.is_hop_by_hop(name):
        raise appinfo_errors.InvalidHttpHeaderName(
            'Only use end-to-end headers may be used. See RFC 2616 section'
            ' 13.5.1.')

      if name in HttpHeadersDict.DISALLOWED_HEADERS:
        raise appinfo_errors.InvalidHttpHeaderName(
            '%s is a disallowed header.' % name)

      return original_name

if not _HTTP_TOKEN_RE.match(name):
        raise appinfo_errors.InvalidHttpHeaderName(
            'An HTTP header must be a non-empty RFC 2616 token.')


      if name in _HTTP_REQUEST_HEADERS:
        raise appinfo_errors.InvalidHttpHeaderName(
            '%r can only be used in HTTP requests, not responses.'
            % original_name)


      if name.startswith('x-appengine'):
        raise appinfo_errors.InvalidHttpHeaderName(
            'HTTP header names that begin with X-Appengine are reserved.')

      if wsgiref.util.is_hop_by_hop(name):
        raise appinfo_errors.InvalidHttpHeaderName(
            'Only use end-to-end headers may be used. See RFC 2616 section'
            ' 13.5.1.')

      if name in HttpHeadersDict.DISALLOWED_HEADERS:
        raise appinfo_errors.InvalidHttpHeaderName(
            '%s is a disallowed header.' % name)

      return original_name

@get('/proxy')
def proxy():
    url = request.GET.get("url")
    headers = ["{0}: {1}".format(k,v) for k,v in request.headers.iteritems() if k.lower() not in STRIP_HEADERS]

    try:
        headtuple, content = curl_http(url, headers)
#        import ipdb;ipdb.set_trace()    
        headret = [(k,v) for k,v in headtuple if not is_hop_by_hop(k)]
        raise HTTPResponse(output = content, header = headret)
    except (pycurl.error, CurlNon200Status):
        redirect(url)

    except Exception, e:
        raise

def filter_request_headers(req, allow_host=False):
    ret = [(k, v) for (k, v) in req.headers.items()\
           if not is_hop_by_hop(k)]
    if allow_host:
        remove_headers = ['content-length']
    else:
        remove_headers = ['content-length', 'host']
    ret = dict(filter(lambda x: x[0].lower() not in remove_headers,
                      ret))
    return ret