code: public Properties getConfigProperties(@Nonnull String packageName) {
      return cache.computeIfAbsent(packageName, s -> {
        StringBuilder buf = new StringBuilder();
        if (!packageName.isEmpty()) {
          buf.append(packageName.replace('.', '/'));
          buf.append('/');
        }
        buf.append(RobolectricTestRunner.CONFIG_PROPERTIES);
        final String resourceName = buf.toString();
  
        try (InputStream resourceAsStream = getResourceAsStream(resourceName)) {
          if (resourceAsStream == null) {
            return null;
          }
          Properties properties = new Properties();
          properties.load(resourceAsStream);
          return properties;
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
      });
    }
docs: Return a {@link Properties} file for the given package name, or {@code null} if none is
  available.
  
  @since 3.2