'Modify the request headers'

def request(self, method, request_uri, headers, content, cnonce=None):

    H = (lambda x: _md5(x).hexdigest())
    KD = (lambda s, d: H(('%s:%s' % (s, d))))
    A2 = ''.join([method, ':', request_uri])
    self.challenge['cnonce'] = (cnonce or _cnonce())
    request_digest = ('"%s"' % KD(H(self.A1), ('%s:%s:%s:%s:%s' % (self.challenge['nonce'], ('%08x' % self.challenge['nc']), self.challenge['cnonce'], self.challenge['qop'], H(A2)))))
    headers['authorization'] = ('Digest    username="%s",    realm="%s",    nonce="%s",    uri="%s",    algorithm=%s,    response=%s,    qop=%s,    nc=%08x,    cnonce="%s"' % (self.credentials[0], self.challenge['realm'], self.challenge['nonce'], request_uri, self.challenge['algorithm'], request_digest, self.challenge['qop'], self.challenge['nc'], self.challenge['cnonce']))
    self.challenge['nc'] += 1
