code: private ContentCryptoMaterial newContentCryptoMaterial(
              EncryptionMaterialsProvider kekMaterialProvider,
              Provider provider, AmazonWebServiceRequest req) {
          EncryptionMaterials kekMaterials = kekMaterialProvider.getEncryptionMaterials();
          if (kekMaterials == null)
              throw new SdkClientException("No material available from the encryption material provider");
          return buildContentCryptoMaterial(kekMaterials, provider, req);
      }
docs: Returns a non-null content encryption material generated with the given kek
  material and security providers.
  
  @throws SdkClientException if no encryption material can be found from
  the given encryption material provider.