Copyright Coredatra LLC, and contributors.
See the AUTHORS file at the top level of this distribution and 
https://github.com/crossfilter/crossfilter-async/blob/master/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
   https://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
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