public static <E> Set<E> newIdentityHashSet() {
    return Sets.newSetFromMap(new IdentityHashMap<E, Boolean>());
  }
Creates an empty {@code Set} that uses identity to determine equality. It compares object
references, instead of calling {@code equals}, to determine whether a provided object matches
an element in the set. For example, {@code contains} returns {@code false} when passed an
object that equals a set member, but isn't the same instance. This behavior is similar to the
way {@code IdentityHashMap} handles key lookups.
fbcore/src/main/java/com/facebook/common/internal/Sets.java