code: private Map<String, String> getConfigMapFromProperties(String prefix) {
          Map<String, String> rval = new HashMap<>();
          getKeys(prefix).forEach(pair -> {
              if (!pair.getKey().equals(prefix)) {
                  String shortKey = pair.getKey().substring(prefix.length() + 1);
                  rval.put(shortKey, pair.getValue());
              }
          });
          return rval;
      }
docs: Gets all properties in the engine configuration that are prefixed
  with the given prefix.
  @param prefix the prefix
  @return all prefixed properties