docs: public static LuaCondition isNull(LuaValue value) {
          LuaAstExpression expression;
          if (value instanceof LuaLocal) {
              expression = new LuaAstLocal(((LuaLocal) value).getName());
          } else {
              throw new IllegalArgumentException("Unexpected value type: " + value.getClass().getName());
          }
          return new LuaCondition(new LuaAstNot(expression));
      }