@Override
        public Set<RequestManager> getDescendants() {
            Set<SupportRequestManagerFragment> descendantFragments = getDescendantRequestManagerFragments();
            HashSet<RequestManager> descendants = new HashSet<RequestManager>(descendantFragments.size());
            for (SupportRequestManagerFragment fragment : descendantFragments) {
                if (fragment.getRequestManager() != null) {
                    descendants.add(fragment.getRequestManager());
                }
            }
            return descendants;
        }
Returns true if the fragment is a descendant of our parent.
core/src/main/java/com/bumptech/glide/manager/SupportRequestManagerFragment.java