Add lenunit option to load

[juliohm]

Related to #100

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.53%. Comparing base (f4cda29) to head (43e4aa2).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #110 +/- ## ========================================== + Coverage 94.47% 94.53% +0.06% ========================================== Files 17 18 +1 Lines 1086 1098 +12 ========================================== + Hits 1026 1038 +12 Misses 60 60 ```

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