Py-pde

What's Changed
* Explicit treatment of normal boundary conditions by david-zwicker in https://github.com/zwicker-group/py-pde/pull/250
* Improved operators for `SphericalSymGrid` by david-zwicker in https://github.com/zwicker-group/py-pde/pull/249
* Improved type hints and docs by david-zwicker in https://github.com/zwicker-group/py-pde/pull/248


**Full Changelog**: https://github.com/zwicker-group/py-pde/compare/v0.19.2...v0.20.0

What's Changed
* Treat NaN in state space in adaptive time stepping by david-zwicker in https://github.com/zwicker-group/py-pde/pull/239
* Added improved adaptive stepper for runge-kutta method by david-zwicker in https://github.com/zwicker-group/py-pde/pull/240
* Enhance docs for the solve method of class pde.pdes.base by lmenou in https://github.com/zwicker-group/py-pde/pull/241
* Improved documentation by david-zwicker in https://github.com/zwicker-group/py-pde/pull/242
* Added a Counter class for a better implementation of JIT_COUNT by david-zwicker in https://github.com/zwicker-group/py-pde/pull/243
* Added method to show mathematical representation of boundary conditions by david-zwicker in https://github.com/zwicker-group/py-pde/pull/245
* Added user-defined boundary conditions by david-zwicker in https://github.com/zwicker-group/py-pde/pull/246
* Improved implementation of UserBC to handle more cases by david-zwicker in https://github.com/zwicker-group/py-pde/pull/247

New Contributors
* lmenou made their first contribution in https://github.com/zwicker-group/py-pde/pull/241

**Full Changelog**: https://github.com/zwicker-group/py-pde/compare/v0.19.1...v0.19.2

What's Changed
* Remove NaN values before smoothing 1D data by david-zwicker in https://github.com/zwicker-group/py-pde/pull/237
* Improved edge cases of SmoothData1D by david-zwicker in https://github.com/zwicker-group/py-pde/pull/238


**Full Changelog**: https://github.com/zwicker-group/py-pde/compare/v0.19.0...v0.19.1

What's Changed
* Removed coordination normalization from transform calls by david-zwicker in https://github.com/zwicker-group/py-pde/pull/214
* Removed temporary pin of pytest version by david-zwicker in https://github.com/zwicker-group/py-pde/pull/215
* Removed unnecessary field copy from ConsistencyTracker by david-zwicker in https://github.com/zwicker-group/py-pde/pull/216
* Removed CartesianGridBase by david-zwicker in https://github.com/zwicker-group/py-pde/pull/218
* Added anti-periodic boundary conditions by david-zwicker in https://github.com/zwicker-group/py-pde/pull/219
* Fixed a bug in the adaptive stepper that occured when error vanished by david-zwicker in https://github.com/zwicker-group/py-pde/pull/223
* Refactored explicit stepper to be structured more clearly by david-zwicker in https://github.com/zwicker-group/py-pde/pull/224
* Updated requirements by david-zwicker in https://github.com/zwicker-group/py-pde/pull/225
* Allowed creating fields from expressions that cannot be vectorized by david-zwicker in https://github.com/zwicker-group/py-pde/pull/228
* Added `evaluate` function by david-zwicker in https://github.com/zwicker-group/py-pde/pull/231

**Full Changelog**: https://github.com/zwicker-group/py-pde/compare/v0.18.0...v0.19.0

What's Changed

* Changed name of default plotting action from "create" to "none".
* Removed the deprecated names `PolarGrid` and `SphericalGrid`
* Added explicit method to convert coordinates between different systems
* Adjusted tests

**Full Changelog**: https://github.com/zwicker-group/py-pde/compare/v0.17.3...v0.18.0

Fixed bug that prevented many operations on new sympy version 1.10.