[CHANGE] Drop support for Python versions 2.7, 3.4, and 3.5. 718
[FEATURE] Support adding labels when using `.time()` 730
[ENHANCEMENT] Begin to add type hints to functions. 705
[ENHANCEMENT] Improved go-to-declaration behavior for editors. 747 
[BUGFIX] Remove trailing slashes from pushgateway URLS. 722
[BUGFIX] Catch non-integer bucket/count values. 726

[FEATURE] Exemplar support (excludes multiprocess) 669 
[ENHANCEMENT] Add support for Python 3.10 706
[ENHANCEMENT] Restricted Registry will handle metrics added after restricting 675, 680  
[ENHANCEMENT] Raise a more helpful error if a metric is not observable 666
[BUGFIX] Fix instance_ip_grouping_key not working on MacOS 687 
[BUGFIX] Fix assertion error from favicion.ico with Python 2.7 715

[CHANGE] Specify that the `labelvalues` argument on metric constructors is internal by renaming it to `_labelvalues`. If you are affected by this change, it is likely that the metric was not being registered. 660
[BUGFIX] `write_to_textfile` will overwrite files in windows. If using python 3.4 or newer the replace will be atomic. 650

[BUGFIX] Support lowercase `prometheus_multiproc_dir` environment variable in `mark_process_dead`. 644

* [CHANGE] Python 2.6 is no longer supported. 592
* [CHANGE] The `prometheus_multiproc_dir` environment variable is deprecated in favor of `PROMETHEUS_MULTIPROC_DIR`. 624
* [FEATURE] Follow redirects when pushing to Pushgateway using `passthrough_redirect_handler`. 622
* [FEATURE] Metrics support a `clear()` method to remove all children. 642
* [ENHANCEMENT] Tag support in GraphiteBridge. 618

[ENHANCEMENT] Add support for python3.9 (600)
[ENHANCEMENT] Various updates for latest OpenMetrics draft spec (576 577)

[FEATURE] Added ASGI application (512)
[FEATURE] Add support for parsing timestamps in Prometheus exposition format. (483)
[FEATURE] Add target_info to registries (453)
[ENHANCEMENT] Handle empty and slashes in label values for pushgateway (547 442)
[ENHANCEMENT] Various updates for latest OpenMetrics draft spec (434 445 538 460 496)
[ENHANCEMENT] Add `HELP` output for auto-created metrics (471)
[ENHANCEMENT] Use mmap.PAGESIZE constant as value for first read. (505)
[ENHANCEMENT] Add `__repr__` method to metric objects, make them debug friendly. (481)
[ENHANCEMENT] Add observability check to metrics (455 520)
[BUGFIX] Fix urlparse in python >= 3.7.6 (497)
[BUGFIX] Cleaning up name before appending unit on name (543)
[BUGFIX] Allow for OSError on Google App Engine (448)

[BUGFIX] multiprocess: don't crash on missing gauge_live/sum files (424)
[BUGFIX] correctly bind method on Python 2.x (403)

[ENHANCEMENT] Multiprocess exposition speed boost (421)
[ENHANCEMENT] optimize openmetrics text parsing (~4x perf) (402)
[ENHANCEMENT] Add python3.7 support (418)
[ENHANCEMENT] Change exemplar length limit to be only for label names+values (397)
[BUGFIX] Disable gcCollector for pypy (380)

[ENHANCEMENT] Better exceptions on exposition failure (364)
[BUGFIX] Fix deadlock in gcCollector, metrics are now different (371)
[BUGFIX] Fix thread leak in Python 3.7 (356)
[BUGFIX] Make the format strings compatible with Python 2.6 (361)
[BUGFIX] parser: ensure samples are of type Sample (358)