code: public <R> R forThose(RFunc2<Boolean, K, V> predicate, RFunc2<R, K, V> func) {
                  return forThose(predicate, Style.$(func));
          }
docs: define a function to deal with each element in the map
  
  @param predicate a function takes in each element from map and returns
  true or false(or null)
  @param func      a function takes in each element from map and returns
  'last loop info'
  @return return 'last loop value'.<br>
  check
  <a href="https://github.com/wkgcass/Style/">tutorial</a> for
  more info about 'last loop value'