code: def import_public_rsa_key_from_file(filename):
      
      with open(filename, "rb") as key_file:
          public_key = serialization.load_pem_public_key(
              key_file.read(),
              backend=default_backend())
      return public_key
docs: Read a public RSA key from a PEM file.
  
      :param filename: The name of the file
      :param passphrase: A pass phrase to use to unpack the PEM file.
      :return: A
          cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey instance