code: def _decrypt(private_key, ciphertext, rsa_oaep_padding=False):
      
  
      if not isinstance(private_key, PrivateKey):
          raise TypeError(pretty_message(
              '''
              private_key must be an instance of the PrivateKey class, not %s
              ''',
              type_name(private_key)
          ))
  
      if not isinstance(ciphertext, byte_cls):
          raise TypeError(pretty_message(
              '''
              ciphertext must be a byte string, not %s
              ''',
              type_name(ciphertext)
          ))
  
      if not isinstance(rsa_oaep_padding, bool):
          raise TypeError(pretty_message(
              '''
              rsa_oaep_padding must be a bool, not %s
              ''',
              type_name(rsa_oaep_padding)
          ))
  
      if _backend == 'winlegacy':
          return _advapi32_decrypt(private_key, ciphertext, rsa_oaep_padding)
      return _bcrypt_decrypt(private_key, ciphertext, rsa_oaep_padding)
docs: Encrypts a value using an RSA private key
  
      :param private_key:
          A PrivateKey instance to decrypt with
  
      :param ciphertext:
          A byte string of the data to decrypt
  
      :param rsa_oaep_padding:
          If OAEP padding should be used instead of PKCS#1 v1.5
  
      :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 plaintext