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Code in python/ray/rllib/{evolution_strategies, dqn} adapted from
https://github.com/openai (MIT License)

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Code in python/ray/rllib/impala/vtrace.py from
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Code in python/ray/rllib/ars is adapted from https://github.com/modestyachts/ARS

Copyright (c) 2018, ARS contributors (Horia Mania, Aurelia Guy, Benjamin Recht)
All rights reserved.

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modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.

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