code: @Override
      public String getFunction(String function, Object... args) {
          if (args == null) {
              return function + "();";
          }
          StringBuilder sb = new StringBuilder();
          sb.append(function).append("(");
          for (Object arg : args) {
              sb.append(getArgString(arg)).append(",");
          }
          sb.replace(sb.length() - 1, sb.length(), ")");
  
          return sb.toString();
      }
docs: Gets a function as a String, which then can be passed to the execute()
  method.
  
  @param function The function to invoke
  @param args Arguments the function requires
  @return A string which can be passed to the JavaScript environment to
  invoke the function