This release includes the following changes:
- #268, #271, #273, #275, #283, #285, #290 Changes support of STIX 2.1 to WD05 (CSD02), for all object types
- #269 Updates id properties to take a spec_version parameter
- #283 Changes the exception class hierarchy
- #289 Adds functions for calculating semantic equivalence of two objects
- #286 Fixes handling of custom observable extensions
- #287 Fixes bug with timestamp precision preservation in MarkingDefinition objects