code: @Override
      public Object invokeFunction(String name, Object... args) throws ScriptException, NoSuchMethodException {
          return invokeMethod(getGlobal(), name, args);
      }
docs: Same as invoke(Object, String, Object...) with {@code null} as the
  first argument.  Used to call top-level procedures defined in scripts.
  
  @param args Arguments to pass to the procedure
  @return The value returned by the procedure
  @throws javax.script.ScriptException if an error occurrs during invocation
  of the method.
  @throws NoSuchMethodException        if method with given name or matching
  argument types cannot be found.
  @throws NullPointerException      if method name is null.