Bird2 installation failing for debian https://bird.network.cz/?download&tdir=debian/

Hi all, I am trying to install bird2 from apt as mention in https://bird.network.cz/?download&tdir=debian/ for debian. Its getting failed, seems to be related to apt key is missing, please advise. "W: GPG error: http://bird.network.cz/debian buster InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B188E2B695BD4743 E: The repository 'http://bird.network.cz/debian buster InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details." Thanks Akshay