code: def _decrypt(private_key, ciphertext, padding):
      
  
      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)
          ))
  
      rsa = None
  
      try:
          buffer_size = libcrypto.EVP_PKEY_size(private_key.evp_pkey)
          buffer = buffer_from_bytes(buffer_size)
  
          rsa = libcrypto.EVP_PKEY_get1_RSA(private_key.evp_pkey)
          res = libcrypto.RSA_private_decrypt(len(ciphertext), ciphertext, buffer, rsa, padding)
          handle_openssl_error(res)
  
          return bytes_from_buffer(buffer, res)
  
      finally:
          if rsa:
              libcrypto.RSA_free(rsa)
docs: Decrypts RSA ciphertext using a private key
  
      :param private_key:
          A PrivateKey object
  
      :param ciphertext:
          The ciphertext - a byte string
  
      :param padding:
          The padding mode to use
  
      :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