code: @SuppressWarnings("unchecked")
      public <A> A createAliasForVariable(Class<A> cl, String var) {
          try {
              Expression<?> path = pathCache.get(Pair.<Class<?>, String>of(cl, var));
              return (A) proxyCache.get(Pair.<Class<?>, Expression<?>>of(cl, path));
          } catch (ExecutionException e) {
              throw new QueryException(e);
          }
      }
docs: Create an alias instance for the given class and variable name
  
  @param <A>
  @param cl type for alias
  @param var variable name for the underlying expression
  @return alias instance