code: public String optString(String name, String fallback) {
  		Object object = opt(name);
  		String result = JSON.toString(object);
  		return result != null ? result : fallback;
  	}
docs: Returns the value mapped by {@code name} if it exists, coercing it if necessary.
  Returns {@code fallback} if no such mapping exists.
  @param name the name of the property
  @param fallback a fallback value
  @return the value or {@code fallback}