docs: private @CheckForNull
      ValueNumber findValueKnownNonnullOnBranch(UnconditionalValueDerefSet fact, Edge edge) {
  
          IsNullValueFrame invFrame = invDataflow.getResultFact(edge.getSource());
          if (!invFrame.isValid()) {
              return null;
          }
          IsNullConditionDecision decision = invFrame.getDecision();
          if (decision == null) {
              return null;
          }
  
          IsNullValue inv = decision.getDecision(edge.getType());
          if (inv == null || !inv.isDefinitelyNotNull()) {
              return null;
          }
          ValueNumber value = decision.getValue();
          if (DEBUG) {
              System.out.println("Value number " + value + " is known nonnull on " + edge);
          }
  
          return value;
      }