code: public Set<String> availableFunctions() {
          Set<String> functions = new HashSet<String>(this.getObjects().keySet());
          Iterator<String> it = functions.iterator();
          while (it.hasNext()) {
              String key = it.next();
              if (!getObject(key).isFunction()) {
                  it.remove();
              }
          }
          return functions;
      }
docs: Returns a set of the functions available
  
  @return a set of the functions available