docs: def extract_public_key(args):
      """ Load an ECDSA private key and extract the embedded public key as raw binary data. """
      sk = _load_ecdsa_signing_key(args)
      vk = sk.get_verifying_key()
      args.public_keyfile.write(vk.to_string())
      print("%s public key extracted to %s" % (args.keyfile.name, args.public_keyfile.name))