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## Description
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## Motivation and Context
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## Types of changes
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- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)

## Checklist:
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- [ ] I have read the [contribution guide](https://github.com/RadioAstronomySoftwareGroup/pyuvdata/blob/master/.github/CONTRIBUTING.md).
- [ ] My code follows the code style of this project.
- [ ] My change requires a change to the documentation.
  - [ ] I have updated the documentation accordingly.
- [ ] My change introduces new functionality that should be highlighted in the tutorial.
  - [ ] I have updated the tutorial accordingly.
- [ ] If this is a bug fix, it includes a new test that breaks as a result of the bug (if possible)
- [ ] If this is a breaking change, it includes backwards compatibility and deprecation warnings (if possible)
- [ ] I have added tests to cover my changes.
- [ ] All new and existing tests pass in both python 2 and python 3.
- [ ] My change requires an update to the [CHANGELOG](https://github.com/RadioAstronomySoftwareGroup/pyuvdata/blob/master/CHANGELOG.md).
  - [ ] I have updated the [CHANGELOG](https://github.com/RadioAstronomySoftwareGroup/pyuvdata/blob/master/CHANGELOG.md) accordingly.