code: private ContentCryptoMaterial newContentCryptoMaterial(
              EncryptionMaterialsProvider kekMaterialProvider,
              Map<String, String> materialsDescription, Provider provider,
              AmazonWebServiceRequest req) {
          EncryptionMaterials kekMaterials =
              kekMaterialProvider.getEncryptionMaterials(materialsDescription);
          if (kekMaterials == null) {
              return null;
          }
          return buildContentCryptoMaterial(kekMaterials, provider, req);
      }
docs: Returns the content encryption material generated with the given kek
  material, material description and security providers; or null if
  the encryption material cannot be found for the specified description.