Update _collections.py to use collections.abc

[kellyjohnson19]

Description

Related Issue

Motivation and Context

How Has This Been Tested?

• make lint
• make docs
• make test-all

Types of changes

• 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:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Licensing:

This project is released under the LICENSE.

• I claim copyrights on my contributions in this pull request, and I provide those contributions via this pull request under the same license terms that the pvl project uses.
• I dedicate any and all copyright interest in my contributions in this pull request to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this contribution under copyright law.