[ Feature ] implement constant labels

[lioshik]

Description

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

• Linter passes correctly
• Add tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

Does this introduce a breaking change?

• Yes
• No

Further comments

[lioshik]

@mga-chka Could you please take a look at this PR when you get a chance?

[mga-chka]

@lioshik I was quite busy the last 2 weeks and this week is a short one (in France), I'll have time next week.