Large portion of the code of Stable-Baselines3 (in `common/`) were ported from Stable-Baselines, a fork of OpenAI Baselines,
both licensed under the MIT License:

before the fork (June 2018):
Copyright (c) 2017 OpenAI (http://openai.com)

after the fork (June 2018):
Copyright (c) 2018-2019 Stable-Baselines Team


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