* fix: Add _registered_method to grpc ChannelStub

* Fix format

* Fix black

Source-Link: googleapis/synthtool@8d392a5
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:a0c4463fcfd9893fc172a3b3db2b6ac0c7b94ec6ad458c7dcea12d9693615ac3

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Source-Link: googleapis/synthtool@d895aec
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:98f3afd11308259de6e828e37376d18867fd321aba07826e29e4f8d9cab56bad

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

* fix(deps): add dependency on proto-plus

* remove unused import

* add common logic for supporting universe domain

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* fix lint issues

* add dependency to oauth2client

* update test cases

* remove dependency to oauth2client

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* fix lint issues

* updates to universe helpers

* update module name and make methods public

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* update lint issues

* address PR comments

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* use empty universe error in test cases

* remove mtls error and add test cases

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* remove is True from test cases

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Source-Link: googleapis/synthtool@85c23b6
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:3741fd1f5f5150378563c76afa06bcc12777b5fe54c5ee01115218f83872134f

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

…630)

Source-Link: googleapis/synthtool@2635888
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:007e7e46ef05e5a32e652bd0062be02f6ff050347d91e0f357b28caab0a042c4

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Victor Chudnovsky <[email protected]>

Source-Link: googleapis/synthtool@db94845
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:a8a80fc6456e433df53fc2a0d72ca0345db0ddefb409f1b75b118dfd1babd952

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Victor Chudnovsky <[email protected]>

* chore(main): release 2.18.0

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>