- Make BaseRunner an abstract base class [\32](https://github.com/python-adaptive/adaptive/issues/32)
- \(BalancingLearner\) loss is cached incorrectly [\31](https://github.com/python-adaptive/adaptive/issues/31)
- LearnerND triangulation incomplete [\29](https://github.com/python-adaptive/adaptive/issues/29)
- \(LearnerND\) flat simplices are sometimes added on the surface of the triangulation [\28](https://github.com/python-adaptive/adaptive/issues/28)
- \(LearnerND\) add iso-surface plot feature [\27](https://github.com/python-adaptive/adaptive/issues/27)
- make BalancingLearner work with the live\_plot [\26](https://github.com/python-adaptive/adaptive/issues/26)
- test\_balancing\_learner\[Learner2D-ring\_of\_fire-learner\_kwargs2\] fails sometimes [\24](https://github.com/python-adaptive/adaptive/issues/24)
- widgets don't show up on adaptive.readthedocs.io [\21](https://github.com/python-adaptive/adaptive/issues/21)
- How to handle NaN? [\18](https://github.com/python-adaptive/adaptive/issues/18)
- Remove public 'fname' learner attribute [\17](https://github.com/python-adaptive/adaptive/issues/17)