hollow/src/main/java/com/netflix/hollow/api/consumer/index/HashIndex.java
public static <T extends HollowRecord> Builder<T> from(HollowConsumer consumer, Class<T> rootType) {
        Objects.requireNonNull(consumer);
        Objects.requireNonNull(rootType);
        return new Builder<>(consumer, rootType);
    }
public static <T extends HollowRecord> Builder<T> from(HollowConsumer consumer, Class<T> rootType) {
        Objects.requireNonNull(consumer);
        Objects.requireNonNull(rootType);
        return new Builder<>(consumer, rootType);
    }
Starts the building of a {@link HashIndex}.

@param consumer the consumer containing instances of the given root type
@param rootType the root type to match and select from
@param <T> the root type
@return a builder