Pre-work for the design change: create own python class for every model

[vinnamkim]

Summary

• This is the pre-work, so that we will actually introduce own python class for every model in the next PR.
• Enrich OTXModel to have export(), register_explain_hook(), and label_info property.
• label_info will be automatically constructed by the input integer argument, num_classes.

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added e2e tests for validation.
• I have added the description of my changes into CHANGELOG in my target branch (e.g., CHANGELOG in develop).​
• I have updated the documentation in my target branch accordingly (e.g., documentation in develop).
• I have linked related issues.

License

• I submit my code changes under the same Apache License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2023 Intel Corporation
# SPDX-License-Identifier: Apache-2.0

[MarkByun]

It looks good.

[sungmanc]

Approved, BTW, could you please explain why do we need to insert the num_classes to the OTXModel at this PR ? I'm not opposite to inject this argument, however, just curiosity. It seems that inserting the num_classes have no much relation with own python class.

[vinnamkim]

Approved, BTW, could you please explain why do we need to insert the num_classes to the OTXModel at this PR ? I'm not opposite to inject this argument, however, just curiosity. It seems that inserting the num_classes have no much relation with own python class.

We introduce LabelInfo as a common property of OTXModel. However, this property affects the shape of the model itself. If we decide it lazily, not at the construction, we should implement this _reset_prediction_layer() as well this time. In addition, lazily resetting the layer seems not good in terms of the clean flow and computation cost.