Automatically detect model format from model file suffix

[ylwu-amzn]

Is your feature request related to a problem?
When user upload a model, they need to input model format. If user input a wrong model format, we will throw exception when load model. But the error message is not so clear. It says "xx.pt file not found" rather than "wrong model format".

What solution would you like?

When user upload model, we can check the file suffix and automatically fill the model format.

What alternatives have you considered?

Another easier short term solution is changing the message to more readable.

Do you have any additional context?
N/A