code: public static TrustingNullnessAnalysis instance(Context context) {
      TrustingNullnessAnalysis instance = context.get(TRUSTING_NULLNESS_KEY);
      if (instance == null) {
        instance = new TrustingNullnessAnalysis();
        context.put(TRUSTING_NULLNESS_KEY, instance);
      }
      return instance;
    }
docs: Retrieve an instance of {@link TrustingNullnessAnalysis} from the {@code context}. If there is
  no {@link TrustingNullnessAnalysis} currently in the {@code context}, create one, insert it,
  and return it.