code: def import_private_key_from_file(filename, passphrase=None):
      
      with open(filename, "rb") as key_file:
          private_key = serialization.load_pem_private_key(
              key_file.read(),
              password=passphrase,
              backend=default_backend())
  
      return private_key
docs: Read a private Elliptic Curve 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.ec.EllipticCurvePrivateKey
          instance