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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 serialize_private_key_to_pem(private_key, passphrase_bytes=None):
 """Serialize private key to PEM. Args: private_key: passphrase_bytes: Returns: bytes: PEM encoded private key """

    return private_key.private_bytes(
        encoding=cryptography.hazmat.primitives.serialization.Encoding.PEM,
        format=cryptography.hazmat.primitives.serialization.PrivateFormat.TraditionalOpenSSL,
        encryption_algorithm=cryptography.hazmat.primitives.serialization.BestAvailableEncryption(
            passphrase_bytes
        )
        if passphrase_bytes is not None
        else cryptography.hazmat.primitives.serialization.NoEncryption(),
    )