'Notify the browser the specified cookie has expired and should be
deleted (via the outgoing HTTP headers)'

def delete_cookie(self, key, path='/', domain=None):

    self.cookies[key] = ''
    if (path is not None):
        self.cookies[key]['path'] = path
    if (domain is not None):
        self.cookies[key]['domain'] = domain
    self.cookies[key]['expires'] = 0
    self.cookies[key]['max-age'] = 0
