code: public static String buildSubscript(Iterable<Object> subscripts) {
          StringBuilder sb = new StringBuilder();
  
          for (Object subscript : subscripts) {
              String value = toString(subscript);
  
              if (value.isEmpty()) {
                  throw new RuntimeException("Null subscript not allowed.");
              }
  
              if (sb.length() > 0) {
                  sb.append(",");
              }
  
              if (StringUtils.isNumeric(value)) {
                  sb.append(value);
              } else {
                  sb.append(QT);
                  sb.append(value.replaceAll(QT, QT2));
                  sb.append(QT);
              }
          }
  
          return sb.toString();
      }
docs: Converts a list of objects to a string of M subscripts.
  
  @param subscripts List to convert.
  @return List of subscripts in M format.