In Model.export(), remove the shape arg and the requirement for the shape to be divisible by 14.

[Abdul-Mukit]

Description

Closes: #396
In main.py, the Model.export() has the argument shape. Developers often try to use it and find it broken. This makes the export process confusing. See: #396 and #99 (comment)

The clean solution is to define resolution during model initialization. Then just call model.export(). Furthermore, the requirement for the input shape to be divisible by 14 is outdated. See: #396 (comment)
All this makes the shape argument in Model.export() call redundant and confusing.

This MR simply proposes to remove this argument and the requirement that the shape be divisible by 14 from the Model.export() call.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How has this change been tested, please provide a testcase or example of how you tested the change?

Tried these and both worked:

from rfdetr import RFDETRSegPreview, RFDETRMedium
model = RFDETRMedium()
mode.export()
model = RFDETRSegPreview()
model.export()

[Abdul-Mukit]

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