other-->Key25519 instance

def get_ecdh_key(self, other):
        '''
        other-->Key25519 instance
        '''
        if self.__secretkey is None:
            raise KeyTypeError('Wrong key type for operation')
        # Copy because curve25519_dh_CreateSharedKey changes secretkey
        tmp_secretkey = ffi.new(C_SECRETKEY, self.secretkey)
        ecdh_key = ffi.new(C_SHAREDKEY)
        lib.curve25519_dh_CreateSharedKey(
            ecdh_key, other.pubkey, tmp_secretkey)
        del tmp_secretkey
        return ffi.get_bytes(ecdh_key)