docs: public void setVariables(List<String> variables)
      {
          if (variables == null || variables.isEmpty())
          {
              this.variables = null;
              return;
          }
  
          Iterator<String> iter = variables.iterator();
          StringBuilder buffer = new StringBuilder(iter.next());
          while (iter.hasNext())
          {
              buffer.append(",").append(iter.next());
          }
          this.variables = buffer.toString();
      }