public Set<SupportRequestManagerFragment> getDescendantRequestManagerFragments() {
        if (rootRequestManagerFragment == null) {
            return Collections.emptySet();
        } else if (rootRequestManagerFragment == this) {
            return Collections.unmodifiableSet(childRequestManagerFragments);
        } else {
            HashSet<SupportRequestManagerFragment> descendants =
                new HashSet<SupportRequestManagerFragment>();
            for (SupportRequestManagerFragment fragment
                : rootRequestManagerFragment.getDescendantRequestManagerFragments()) {
                if (isDescendant(fragment.getParentFragment())) {
                    descendants.add(fragment);
                }
            }
            return Collections.unmodifiableSet(descendants);
        }
    }
Returns the set of fragments that this RequestManagerFragment's parent is a parent to. (i.e. our parent is
the fragment that we are annotating).
core/src/main/java/com/bumptech/glide/manager/SupportRequestManagerFragment.java