implement TraitInstance to inherit directly from TraitHandler

[shoeb-github]

contributes to #697

• copied the methods fromThisClass to TraitInstance.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@2e5a601). Click here to learn what that means.
The diff coverage is 33.33%.

@@            Coverage Diff            @@
##             master     #761   +/-   ##
=========================================
  Coverage          ?   71.73%           
=========================================
  Files             ?       51           
  Lines             ?     6337           
  Branches          ?     1281           
=========================================
  Hits              ?     4546           
  Misses            ?     1393           
  Partials          ?      398

Impacted Files	Coverage Δ
traits/trait_handlers.py	58.48% <33.33%> (ø)

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[mdickinson]

Please remove the validate_none and info_none methods. Apart from that, this LGTM

[mdickinson]

I think this method can be removed: info_none is only used in ThisClass.__init__.

[mdickinson]

This method isn't needed.

[mdickinson]

LGTM, if the CI agrees.

[shoeb-github]

Apart from validate_none and info_none methods, I also removed validate_failed method.

[mdickinson]

I also removed validate_failed method.

Yep, I think that's reasonable. My only worry about that would be subclasses of TraitInstance that rely on validate_failed, but I can't see any place where TraitInstance is subclassed in ETS, and it's unlikely to be used at all outside ETS.