\begin{figure}[t!]
    \centering
    \subfigure{
    \centering
    \includegraphics[width=.23\linewidth]{figure/appendix/gradcam/gradcam_12x12_c3_sd3_key_1.png}
    }\hfil
    \subfigure{
    \centering
    \includegraphics[width=.23\linewidth]{figure/appendix/gradcam/gradcam_12x12_c3_sd3_key_2.png}
    }\hfil
    \subfigure{
    \centering
    \includegraphics[width=.23\linewidth]{figure/appendix/gradcam/gradcam_12x12_c3_sd3_door_1.png}
    }\hfil
    \subfigure{
    \centering
    \includegraphics[width=.23\linewidth]{figure/appendix/gradcam/gradcam_12x12_c3_sd3_door_2.png}
    }\hfil
    \caption{{Additional GradCAM visualization.}}
    \label{fig:appendix_gradcam}
\end{figure}
