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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def import_private_key_from_file(filename, passphrase=None):
 """ 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 """

    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