Python Toolbox includes third-party Python packages as subpackages that are used internally. (These are in the `third_party` package.) These are:

* `Envelopes` by Tomasz Wójcik and others, MIT license.

* `sortedcontainers` by Grant Jenks and others, Apache license 2.0.

* `unittest2` by Robert Collins and others, BSD license.

* `decorator` by Michele Simionato and others, BSD license.

* `pathlib` by Antoine Pitrou and others, MIT license.

* `enum` by Ben Finney and others, PSF license.

* `funcsigs` by Aaron Iles and others, Apache license 2.0.

* `linecache2` by "Testing-cabal" and others, PSF license.

* `traceback2` by "Testing-cabal" and others, PSF license.

* `six` by Benjamin Peterson and others, MIT license.

* `functools` and `collections` by Python-dev and others, PSF license.