@lightproject, It's actually rather short and to the point:

        """ Derive private key from the brain key and the current sequence
            number
        """
        a = py23_bytes(self.account + self.role + self.password, 'utf8')
        s = hashlib.sha256(a).digest()
        return PrivateKey(hexlify(s).decode('ascii'), prefix=self.prefix)

specifically, that's get_private from the method other than that it just sets the public function

Unless you meant you wanted me to step through that too :)