new_contents: 
  var storage = {};
  
  module.exports = function(key, value) {
  	if(!value) return getter(key);
  	setter(key, value);
  };
  
  
  function setter(key, value) {
  	var model = storage[key] || factory(key, value);
  	var nb =  (model.values[value] || 0) + 1;
  	model.values[value] = nb;
  	var max = model.values[model.entity];
  	if(nb > max) storage[key].entity = value;
  }
  
  function factory(key, value) {
  	var model = {
  		entity: value,
  		values: {}
  	};
  	storage[key] = model;
  	return model;
  }
  
  
  
  function getter(key) {
  	return storage[key].entity;
  }
  
subject: set and return preferred values