Use only gitlab ReferenceTag instead of UserList

[CelianR]

What does this PR do?

In order to write a !reference [...] in a yaml file, we have to use UserList which is not explicit.
Used ReferenceTag instead of this and added string representation and a way to iterate through it.

No code has to be changed since functions visiting the YAML tree do not need to visit the content of a reference list.

Motivation

Additional Notes

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

s = StringIO()
yaml.safe_dump(ReferenceTag(['hello', 'world']), s)
print(s.getvalue()) # !reference [hello, world]

[CelianR]

This was useless before, only the static methods were called

[agent-platform-auto-pr]

[Fast Unit Tests Report]

On pipeline 40206946 (CI Visibility). The following jobs did not run any unit tests:

Jobs:

• tests_deb-arm64-py3
• tests_deb-x64-py3
• tests_flavor_dogstatsd_deb-x64
• tests_flavor_heroku_deb-x64
• tests_flavor_iot_deb-x64
• tests_rpm-arm64-py3
• tests_rpm-x64-py3
• tests_windows-x64

If you modified Go files and expected unit tests to run in these jobs, please double check the job logs. If you think tests should have been executed reach out to #agent-devx-help

[chouetz]

I think to remember the initial usage of UserList was to save creation of the __iter__ and __str__.
I'm fine with a definition in ReferenceTag, thanks!

[pr-commenter]

Regression Detector

Regression Detector Results

Run ID: 30c99b42-dd41-4a54-b7d7-872f947b5099 Metrics dashboard Target profiles

Baseline: 44bbe07
Comparison: 6f9cf15

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

No significant changes in experiment optimization goals

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

There were no significant changes in experiment optimization goals at this confidence level and effect size tolerance.

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	links
➖	tcp_syslog_to_blackhole	ingress throughput	+4.27	[-8.82, +17.36]	Logs
➖	pycheck_1000_100byte_tags	% cpu utilization	+0.68	[-4.16, +5.51]	Logs
➖	idle	memory utilization	+0.67	[+0.64, +0.70]	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.00	[-0.01, +0.01]	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.00	[-0.00, +0.00]	Logs
➖	file_tree	memory utilization	-0.47	[-0.53, -0.41]	Logs
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	-0.70	[-1.59, +0.19]	Logs
➖	basic_py_check	% cpu utilization	-0.85	[-3.35, +1.66]	Logs
➖	otel_to_otel_logs	ingress throughput	-1.03	[-1.83, -0.22]	Logs

Explanation

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

[CelianR]

/merge

[dd-devflow]

🚂 MergeQueue: pull request added to the queue

The median merge time in main is 22m.

Use /merge -c to cancel this operation!