code: public void run(List<Variant> variantList) {
          for (int i = 0; i < variantList.size(); i++) {
              List<PopulationFrequency> populationFrequencies = getPopulationFrequencies(variantList.get(i));
              // Update only if there are annotations for this variant. customAnnotation may be empty if the variant
              // exists in the vcf but the info field does not contain any of the required attributes
              if (populationFrequencies != null && populationFrequencies.size() > 0) {
                  VariantAnnotation variantAnnotation = variantList.get(i).getAnnotation();
                  if (variantAnnotation != null) {
                      // variantList and variantAnnotationList must contain variants in the SAME order: variantAnnotation
                      // at position i must correspond to variant i
                      variantAnnotation.setPopulationFrequencies(populationFrequencies);
                  }
              }
          }
      }
docs: Updates VariantAnnotation objects in variantAnnotationList.
  
  @param variantList List of Variant objects. variantList and variantAnnotationList must contain variants in the
  SAME order: variantAnnotation at position i must correspond to variant i