code: public <R> R forEach(RFunc3<R, K, V, IteratorInfo<R>> func) {
                  return forEach(Style.$(func));
          }
docs: define a function to deal with each entry in the map
  
  @param func a function takes in each entry from map and iterator
  info<br>
  and returns 'last loop result'
  @return return 'last loop value'.<br>
  check
  <a href="https://github.com/wkgcass/Style/">tutorial</a> for
  more info about 'last loop value'
  @see IteratorInfo