code: private void checkNonNullReturnValue(XMethod thisMethod, Location location, ValueNumberFrame vnaFrame,
              UnconditionalValueDerefSet fact) throws DataflowAnalysisException {
          INullnessAnnotationDatabase database = AnalysisContext.currentAnalysisContext().getNullnessAnnotationDatabase();
  
          if (database.getResolvedAnnotation(thisMethod, true) != NullnessAnnotation.NONNULL) {
              return;
          }
          if (reportPotentialDereference(location, invDataflow.getFactAtLocation(location))) {
              ValueNumber vn = vnaFrame.getTopValue();
              fact.addDeref(vn, location);
          }
      }
docs: If this is a method call instruction, check to see if any of the
  parameters are @NonNull, and treat them as dereferences.
  
  @param location
  the Location of the instruction
  @param vnaFrame
  the ValueNumberFrame at the Location of the instruction
  @param fact
  the dataflow value to modify
  
  @throws DataflowAnalysisException