docs: public String generateNewVarName(String baseName, int argIndex) {
          if (!variables.containsKey(baseName) && argIndex == 0) {
              return baseName;
          }
  
          //need to find a new name
          int count = 0;
          String name = baseName + (count == 0 ? "" : "_" + count) + (argIndex > 0 ? ":" + argIndex : "");
          while (getVariable(name) != null) {
              name = baseName + "_" + (++count) + (argIndex > 0 ? ":" + argIndex : "");
          }
  
          if (getVariable(name) != null) {
              throw new ND4JIllegalStateException("Converged on already generated variable!");
          }
          return name;
      }