code: public static Set<VariantType> subTypes(VariantType variantType) {
          if(variantType.equals(VariantType.SNV)) {
              return Collections.singleton(VariantType.SNP);
          } else if (variantType.equals(VariantType.MNV)) {
              return Collections.singleton(VariantType.MNP);
          } else if (variantType.equals(VariantType.SV)) {
              return  SV_SUBTYPES;
          } else {
              return Collections.emptySet();
          }
      }
docs: Return all VariantTypes subtypes given a VariantType.
  {@link VariantType} represents a hierarchical structure where SNV includes all SNP, MNV includes MNP
  and SV includes  INSERTION, DELETION, TRANSLOCATION, INVERSION and CNV
  
  @param variantType   Variant Type
  @return  Set of subtypes