code: private RegionMetadata loadFromSystemProperty() {
          final String overrideFilePath = System.getProperty
                  (REGIONS_FILE_OVERRIDE);
  
          if (overrideFilePath != null) {
              try {
                  return LegacyRegionXmlLoadUtils.load(new File
                          (overrideFilePath));
              } catch (IOException exception) {
                  throw new SdkClientException(
                          "Error parsing region metadata from " + overrideFilePath,
                          exception);
              }
          }
          return null;
      }
docs: Loads region metadata from file location specified in
  {@link #REGIONS_FILE_OVERRIDE} property.
  Returns null if no such property exists.
  
  @throws SdkClientException if any error occurs while loading the
  metadata file.