code: def load_pem(cls, private_key, password=None):
          
          # TODO(sam): try to break this in tests
          maybe_path = normpath(private_key)
          if os.path.isfile(maybe_path):
              with open(maybe_path, 'rb') as pkf:
                  private_key = pkf.read()
          if not isinstance(private_key, six.binary_type):
              private_key = private_key.encode('utf-8')
  
          pkey = serialization.load_pem_private_key(
              private_key,
              password=password,
              backend=crypto_backends.default_backend())
          return cls(pkey)
docs: Return a PrivateKey instance.
  
          :param private_key: Private key string (PEM format) or the path
                              to a local private key file.