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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_public_rsa_key_from_file(filename):
 """ 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 """

    with open(filename, "rb") as key_file:
        public_key = serialization.load_pem_public_key(
            key_file.read(),
            backend=default_backend())
    return public_key