This release includes the following changes:
- Most (if not all) STIX 2.1 SDOs/SROs and core objects have been implemented according to the latest CSD/WD document
- There is an implementation for the conversion scales
- #196, #193 Removing duplicate code for: properties, registering objects, parsing objects, custom objects
- #80, #197 Most (if not all) tests created for v20 are also implemented for v21
- #189 Added extra checks for the pre-commit tool
- #202 It is now possible to pass a Bundle into add() method in Memory datastores