def modified(date=None, etag=None):
    try:
        from __builtin__ import set
    except ImportError:
        # for python 2.3
        from sets import Set as set

    n = set([x.strip('" ') for x in web.ctx.env.get('HTTP_IF_NONE_MATCH', '').split(',')])
    m = net.parsehttpdate(web.ctx.env.get('HTTP_IF_MODIFIED_SINCE', '').split(';')[0])
    validate = False
    if etag:
        if '*' in n or etag in n:
            validate = True
    if date and m:
        # we subtract a second because 
        # HTTP dates don't have sub-second precision
        if date-datetime.timedelta(seconds=1) <= m:
            validate = True
    
    if date: lastmodified(date)
    if etag: web.header('ETag', '"' + etag + '"')
    if validate:
        raise web.notmodified()
    else:
        return True
Checks to see if the page has been modified since the version in the
dataset/ETHPy150Open rouge8/20questions/web/http.py/modified