None of the models support dynamic batch size

[tungngreen]

Despite what's shown in export.py

dynamic_axes={'images': {0: 'batch', 2: 'height', 3: 'width'},  # size(1,3,640,640)
    'outputs': {0: 'batch', 2: 'y', 3: 'x'}} if opt.dynamic else None)

the models do not support dynamic batching.

Even if argument --dynamic is parsed, the batch size is still fixed for all of the outputs.