remove unused variable and doc

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extra : rebase_source : 7cb8037b9b59ca6168bb554071bd9bb185fe04c6
Cache zgt and make more methods use it for speed

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extra : rebase_source : e6fd84758051597c5ed6e4e0f8a50fd6a95f4975
more optimization

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extra : rebase_source : b370b4cb0679a1ddefe91af7872b3b4164b91fd6
Comments for party mode

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extra : rebase_source : 2d3b9e2b0e0d8dd7c65e9fb874014ac1ffb1441e
pylint

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extra : rebase_source : d9440fdb7f9abea8848691ed779f4aa868c02f44
pylint

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extra : rebase_source : 235b0124736774f580239a2b596b9b7428467ef1
Return sets not iterables

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extra : rebase_source : cbec8b213bd68e4958c7b8b862d09b713387ed22
Merge pull request #141 from lawrenceakka/topology-fixes

Fixes to new topology code. I'll merge myself since this changes litre except making things rather faster!