Add tests using mocker to main.py

[sweep-nightly]

Description

This PR adds tests using mocker to the main.py file in order to ensure the correctness of the data loading, preprocessing, and model definition.

Summary of Changes

• Created a new test file, test_main.py, in the src directory.
• Imported the necessary modules for testing, including pytest, mocker from pytest_mock, torch, torchvision.transforms, torch.utils.data.DataLoader, and the relevant functions and classes from main.py.
• Added a function to test the data loading and preprocessing. This function uses the mocker to mock the DataLoader and transforms.Compose functions and checks that the mocked functions were called with the expected arguments.
• Added a function to test the model definition. This function calls the model definition code from main.py and checks that the returned model is an instance of the expected class and has the expected structure.
• Added docstrings to each function explaining what the function tests and how it does so.
• Ensured that the code is properly formatted and indented, and that variable and function names are descriptive and follow a consistent naming convention.

Please review and merge this PR to incorporate the tests using mocker into the main.py file.

Fixes #10.

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Rollback Files For Sweep

• Rollback changes to src/test_main.py
• Rollback changes to src/test_main.py

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