code: public void purgeDeletedKey(String vaultBaseUrl, String keyName) {
          purgeDeletedKeyWithServiceResponseAsync(vaultBaseUrl, keyName).toBlocking().single().body();
      }
docs: Permanently deletes the specified key.
  The Purge Deleted Key operation is applicable for soft-delete enabled vaults. While the operation can be invoked on any vault, it will return an error if invoked on a non soft-delete enabled vault. This operation requires the keys/purge permission.
  
  @param vaultBaseUrl The vault name, for example https://myvault.vault.azure.net.
  @param keyName The name of the key
  @throws IllegalArgumentException thrown if parameters fail the validation
  @throws KeyVaultErrorException thrown if the request is rejected by server
  @throws RuntimeException all other wrapped checked exceptions if the request fails to be sent