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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
https://github.com/deepmind/scalable_agent

Copyright 2018 Google LLC

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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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------------------
Code in python/ray/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
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.