def _toString_AGENTV3(self):
        """
        Return a private Secure Shell Agent v3 key.  See
        _fromString_AGENTV3 for the key format.

        @rtype: L{bytes}
        """
        data = self.data()
        if not self.isPublic():
            if self.type() == 'RSA':
                values = (data['e'], data['d'], data['n'], data['u'],
                          data['p'], data['q'])
            elif self.type() == 'DSA':
                values = (data['p'], data['q'], data['g'], data['y'],
                          data['x'])
            return common.NS(self.sshType()) + b''.join(map(common.MP, values))

        Return a private Secure Shell Agent v3 key.  See
        _fromString_AGENTV3 for the key format.

        @rtype: L{bytes}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/ssh/keys.py