AMP check image download backup

[glenn-jocher]

Resolves #7931

🛠️ PR Summary

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🌟 Summary

Improvement of Automatic Mixed Precision (AMP) checking with enhanced image loading logic.

📊 Key Changes

• Added file existence check before reading the 'bus.jpg' image.
• Incorporated online image retrieval if the local image is not available.
• Maintains AMP functionality if neither local nor online image can be loaded.

🎯 Purpose & Impact

• Robustness: Ensures the AMP check can always be performed, either with a local or an online fallback image.
• User Experience: Prevents errors that would occur if the local test image is missing, allowing for a smoother experience.
• Performance: AMP checks proceed correctly, potentially enabling faster and more efficient model training and inference when supported.