Add an interface to turn objects read-only #3786

	# This workflow is used to check backwards compatibility

	name: Backwards

	on:
	push:
	branches: [ main ]
	pull_request:
	branches: [ main ]

	jobs:
	build:

	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@v2
	- name: Setup environment
	run: \|
	python .ci_support/condamerge.py --base .ci_support/environment.yml --add .ci_support/environment-notebooks.yml > environment.yml
	- name: Setup Mambaforge
	uses: conda-incubator/setup-miniconda@v2
	with:
	python-version: '3.10'
	miniforge-variant: Mambaforge
	channels: conda-forge
	channel-priority: strict
	activate-environment: my-env
	use-mamba: true
	- name: Set cache date and number
	run: \|
	echo "DATE=$(date +'%Y%m%d')" >> $GITHUB_ENV
	cat .github/variables/cache_number.env >> $GITHUB_ENV
	- uses: actions/cache@v2
	with:
	path: /usr/share/miniconda3/envs/my-env
	key: linux-64-py-3-10-conda-${{ hashFiles('environment.yml') }}-${{ env.DATE }}-${{ env.CACHE_NUMBER }}
	id: cache
	- name: Update environment
	run: mamba env update -n my-env -f environment.yml
	if: steps.cache.outputs.cache-hit != 'true'
	- name: Setup
	shell: bash -l {0}
	run: \|
	python .ci_support/pyironconfig.py
	- name: Test
	shell: bash -l {0}
	run: ./.ci_support/test_backwards.sh

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