553 feature refactor segmentationdataset class

[valhassan]

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Description

Fixes #553

Type of change

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• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Other

How Has This Been Tested?

added unit test for SegmentionDataset class

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[remtav]

nicely done. What was the initial motivation for this refactoring @valhassan ? Adding a test :) ?