code: @Deprecated
      public Object eval(final String code, final Object... args) {
          CommandResult result = doEval(code, args);
          result.throwOnError();
          return result.get("retval");
      }
docs: Calls {@link DB#doEval(java.lang.String, java.lang.Object[]) }. If the command is successful, the "retval" field is extracted and
  returned. Otherwise an exception is thrown.
  
  @param code {@code String} representation of JavaScript function
  @param args arguments to pass to the JavaScript function
  @return result of the execution
  @throws MongoException if the operation failed
  @mongodb.driver.manual reference/method/db.eval/ db.eval()
  @deprecated The eval command was deprecated in MongoDB 3.0