I have the following MWE. and I want to fade this square, the caption and everything that I will put in the square.

```
    \documentclass{standalone}
\usepackage[T1]{fontenc} 
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\begin{document}    
\begin{tikzpicture}
% % % % % Rectangle Model 
    \node (sensor) at (-6.5,-10){};
    \node (sensor_rect1) at (-4.25,-7.25){};
    \node (sensor_rect2) at (-8.75,-12){};
    \draw[line width=2pt,rounded corners=1cm] (sensor_rect1) rectangle (sensor_rect2);
    \node at (-6.5,-10.5) {\textbf{content  here}};
    \node at (-6.5,-12.25){\textbf{  model}};
\end{tikzpicture}
\end{document}

```

[![enter image description here](https://i.stack.imgur.com/Oj55E.png)](https://i.stack.imgur.com/Oj55E.png)