docs: public Set<Processor<?, ?>> getAllProcessors() {
          IdentityHashMap<Processor<?, ?>, Void> all = new IdentityHashMap<>();
          for (ProcessorGraphNode<?, ?> root: this.roots) {
              for (Processor p: root.getAllProcessors()) {
                  all.put(p, null);
              }
          }
          return all.keySet();
      }