make Collection subclassable

[lsaffre]

I would like to extend the invoke.Collection class by subclassing it. But the from_module method in the current version will always return the original class. This little patch has no influence on the API, is cleaner, and would make me happy :-)

[codecov-io]

Current coverage is 92.78%

Merging #342 into master will decrease coverage by -0.67% as of 566c109

@@            master    #342   diff @@
======================================
  Files           20      20       
  Stmts         1773    1773       
  Branches       305     304     -1
  Methods          0       0       
======================================
- Hit           1657    1645    -12
+ Partial         34      33     -1
- Missed          82      95    +13

Review entire Coverage Diff as of 566c109

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[bitprophet]

Thanks, that's an oversight/bug for sure, adding to milestone :)

[bitprophet]

Years later...sob...merged this & made sure it played nice with how the code changed in the interim. (tl;dr we moved things around & are using an inner closure, but were still hardcoding Collection instead of cls.)

[lsaffre]

Great! Thanks!