code: public JSONArray optJSONArray(int index) {
  		Object object = opt(index);
  		return object instanceof JSONArray ? (JSONArray) object : null;
  	}
docs: Returns the value at {@code index} if it exists and is a {@code
  JSONArray}. Returns null otherwise.
  @param index the index to get the value from
  @return the array at {@code index} or {@code null}