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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/_private/prometheus_exporter.py is adapted from https://github.com/census-instrumentation/opencensus-python/blob/master/contrib/opencensus-ext-prometheus/opencensus/ext/prometheus/stats_exporter/__init__.py

# Copyright 2018, OpenCensus Authors
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Code in python/ray/tests/modin/test_modin and
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- http:https://github.com/modin-project/modin/master/modin/pandas/test/test_general.py
- http:https://github.com/modin-project/modin/master/modin/pandas/test/utils.py

Copyright (c) 2018-2020 Modin Developers.

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Code in python/ray/_private/runtime_env/_clonevirtualenv.py is adapted from https://github.com/edwardgeorge/virtualenv-clone/blob/master/clonevirtualenv.py

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---------------------------------------------------------------------------------------------------------------
Code in python/ray/_private/thirdparty/tabulate/tabulate.py is adapted from https://github.com/astanin/python-tabulate/blob/4892c6e9a79638c7897ccea68b602040da9cc7a7/tabulate.py

Copyright (c) 2011-2020 Sergey Astanin and contributors

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