code: public Observable<KeyBundle> deleteKeyAsync(String vaultBaseUrl, String keyName) {
          return deleteKeyWithServiceResponseAsync(vaultBaseUrl, keyName).map(new Func1<ServiceResponse<KeyBundle>, KeyBundle>() {
              @Override
              public KeyBundle call(ServiceResponse<KeyBundle> response) {
                  return response.body();
              }
          });
      }
docs: Deletes a key of any type from storage in Azure Key Vault. The delete key operation cannot be used to remove individual versions of a key. This operation removes the cryptographic material associated with the key, which means the key is not usable for Sign/Verify, Wrap/Unwrap or Encrypt/Decrypt operations. Authorization: Requires the keys/delete permission.
  
  @param vaultBaseUrl The vault name, for example https://myvault.vault.azure.net.
  @param keyName The name of the key to delete.
  @return the observable to the KeyBundle object