code: static void setArrayIndex(Map<String,String> meta, int level, int index) {
          meta.put(level + ARRAY_IDX_SUFFIX, Integer.toString(index));
      }
docs: Sets an array index on a map of metadata for a specific level of a nested
  json tree. Since the json requires that arrays have preserved order, it's
  imported that it is constrained from the flattened to the re-expanded
  representation.
  @param meta
  @param level
  @param index