Feat/boundary dataloader

[sadamov]

FEEL FREE TO GIVE FEEDBACK, BUT NOT READY FOR FULL REVIEW!

Describe your changes

< Summary of the changes.>

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< List any dependencies that are required for this change. >

Issue Link

< Link to the relevant issue or task. > (e.g. closes #00 or solves #00)

Type of change

• [ ] 🐛 Bug fix (non-breaking change that fixes an issue)
• [ ] ✨ New feature (non-breaking change that adds functionality)
• [ ] 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] 📖 Documentation (Addition or improvements to documentation)

Checklist before requesting a review

• [ ] My branch is up-to-date with the target branch - if not update your fork with the changes from the target branch (use pull with --rebase option if possible).
• [ ] I have performed a self-review of my code
• [ ] For any new/modified functions/classes I have added docstrings that clearly describe its purpose, expected inputs and returned values
• [ ] I have placed in-line comments to clarify the intent of any hard-to-understand passages of my code
• [ ] I have updated the README to cover introduced code changes
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have given the PR a name that clearly describes the change, written in imperative form (context).
• [ ] I have requested a reviewer and an assignee (assignee is responsible for merging). This applies only if you have write access to the repo, otherwise feel free to tag a maintainer to add a reviewer and assignee.

Checklist for reviewers

Each PR comes with its own improvements and flaws. The reviewer should check the following:

• [ ] the code is readable
• [ ] the code is well tested
• [ ] the code is documented (including return types and parameters)
• [ ] the code is easy to maintain

Author checklist after completed review

• [ ] I have added a line to the CHANGELOG describing this change, in a section reflecting type of change (add section where missing):
  • added: when you have added new functionality
  • changed: when default behaviour of the code has been changed
  • fixes: when your contribution fixes a bug

Checklist for assignee

• [ ] PR is up to date with the base branch
• [ ] the tests pass
• [ ] author has added an entry to the changelog (and designated the change as added, changed or fixed)
• Once the PR is ready to be merged, squash commits and merge the PR.