code: def load_rsa_public_key_file(rsakeyfile):
      # type: (str, str) ->
      #        cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey
      
      keypath = os.path.expandvars(os.path.expanduser(rsakeyfile))
      with open(keypath, 'rb') as keyfile:
          return cryptography.hazmat.primitives.serialization.\
              load_pem_public_key(
                  keyfile.read(),
                  backend=cryptography.hazmat.backends.default_backend()
              )
docs: Load an RSA Public key PEM file
      :param str rsakeyfile: RSA public key PEM file to load
      :rtype: cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey
      :return: RSAPublicKey