feat: set functions and tests

[ohrechykha]

[ohrechykha]

This is funny: when doing [err=f"Expected ragged type but got {type(x)}", raise TypeError(err)] in specified lines, mypy says it's an unreachable statement. When I switch this back to [raise TypeError(f"Expected ragged type but got {type(x)}")] ruff says exception must be assigned to variable first...