Add Mira sex prediction model

[ieee8023]

From: https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(23)00032-4/fulltext

[Copilot]

Pull Request Overview

This PR adds a MIRA sex prediction model for predicting patient sex from chest X-ray images. The model implements a ResNet34 architecture trained on the CheXpert dataset and provides binary classification between "Male" and "Female" categories.

• Implements a new SexModel class within the MIRA baseline models module
• Adds comprehensive test coverage for the new model functionality
• Integrates the MIRA module into the baseline models package structure

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
torchxrayvision/baseline_models/mira/init.py	New SexModel implementation with ResNet34 architecture and weight loading
torchxrayvision/baseline_models/init.py	Imports the new mira module
tests/test_mira_sex_comprehensive.py	Comprehensive test suite for the SexModel functionality
tests/test_covid_dataloader.py	Adds skip markers to existing tests
tests/test_baseline_models.py	Adds tests for the new MIRA sex model

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