Trigger code to get issue revision (major or minor)?

Hello team!

Could somebody share a code to get issue revision (major or minor)?

delta.getFieldValue("Revision") or delta.getFieldValue.("Major Version ID") returns null if use inside a trigger code.

But.... if use computed field this pattern works ok .... "toText(getFieldValue(ID, "Major Version ID"))"

What SSE grurs could suggest?

Many thanks!