[MINOR]remove deprecated attribute representation

[hungple]

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[R4ML-CI]

Can one of the admins verify this patch?

[hungple]

I have removed deprecated attribute "representation", and used "slots" instead.

[bdwyer2]

Jenkins, ok to test Jenkins, add to whitelist

[R4ML-CI]

Build triggered.

[bdwyer2]

@hungple looks good thanks!

Do you think you could also fix the spelling of "pacakge" in README.md with this PR?

[R4ML-CI]

Build success. All unit tests passed.

[hungple]

@bdwyer2 I have fixed the spelling of "pacakge" in README.md and 2 other files.

[R4ML-CI]

Build triggered.

[R4ML-CI]

Build success. All unit tests passed.