code: @Override
  	public AppEngineGetScalar<E, R> filter(Filter<?>... filters) {
  		if (filters == null) {
  			throw new IllegalArgumentException("'filters' must not be [" + filters + "]");
  		}
  		
  		this.filters = Arrays.asList(filters);
  		return this;
  	}
docs: Qualifies entities to be retrieved with the specified {@code Filter}s.
  Each of the specified filters is combined with "logical and".
  
  @param filters {@code Filter}s to qualify the retrieved entities.
  @return The {@code GetScalar} which the execution result passed to
  {@code Aggregation#aggregate(java.util.List)} is qualified by the
  specified filters.