def rsa_pkcs1v15_decrypt(private_key, ciphertext):
return _decrypt(private_key, ciphertext)<EOL>
Decrypts a byte string using an RSA private key. Uses PKCS#1 v1.5 padding.

:param private_key:
    A PrivateKey object

:param ciphertext:
    A byte string of the encrypted data

:raises:
    ValueError - when any of the parameters contain an invalid value
    TypeError - when any of the parameters are of the wrong type
    OSError - when an error is returned by the OS crypto library

:return:
    A byte string of the original plaintext