What's Changed
* add drop, prepend and append methods to sequence by ChRen95 in https://github.com/pyroll-project/pyroll-core/pull/187
* Clarify definition of chemical composition by ChRen95 in https://github.com/pyroll-project/pyroll-core/pull/188
* added astm grain size class by ChRen95 in https://github.com/pyroll-project/pyroll-core/pull/186
* Added hooks and implementations to CoolingPipe by ChRen95 in https://github.com/pyroll-project/pyroll-core/pull/191
* fix matplotlib image export error due to closed stream by axtimhaus in https://github.com/pyroll-project/pyroll-core/pull/192
**Full Changelog**: https://github.com/pyroll-project/pyroll-core/compare/v2.1.4...v2.1.5