code: public Observable<IssuerBundle> deleteCertificateIssuerAsync(String vaultBaseUrl, String issuerName) {
          return deleteCertificateIssuerWithServiceResponseAsync(vaultBaseUrl, issuerName).map(new Func1<ServiceResponse<IssuerBundle>, IssuerBundle>() {
              @Override
              public IssuerBundle call(ServiceResponse<IssuerBundle> response) {
                  return response.body();
              }
          });
      }
docs: Deletes the specified certificate issuer.
  The DeleteCertificateIssuer operation permanently removes the specified certificate issuer from the vault. This operation requires the certificates/manageissuers/deleteissuers permission.
  
  @param vaultBaseUrl The vault name, for example https://myvault.vault.azure.net.
  @param issuerName The name of the issuer.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the IssuerBundle object