public static HashSet <Beer> GetBeersContainingTags(List <Tag> tags)
{
BeerRepository br = new BeerRepository();
var beers = br.RetrieveAll();
HashSet <Beer> foundBeers = new HashSet <Beer>();
foreach (var tag in tags)
{
foundBeers.UnionWith(br.RetrieveBeersByTag(tag));
}
return(foundBeers);
}