@SuppressWarnings("unchecked")
    protected R transform(Multimap<K, Group> groups) {
        return (R) groups;
    }
Provides aggregated results as a map

@author Jan-Willem Gmelig Meyling

@param <K> multi map key type
@param <V> multi map value type
@param <R> multi map type
querydsl-guava/src/main/java/com/querydsl/core/group/guava/GroupByMultimap.java