code: public VMTransitionBuilder getBuilder(VMState srcState, VMState dstState) {
          Map<VMState, VMTransitionBuilder> dstCompliant = vmAMB2.get(dstState);
          if (dstCompliant == null) {
              return null;
          }
          return dstCompliant.get(srcState);
      }
docs: Get the model builder for a given transition
  
  @param srcState the current VM state
  @param dstState the current VM state
  @return the list of possible transitions. {@code null} if no transition is available