The use of a metaclass on the view prevents mixing in the FilterMixin with Views that use a metaclass for other purposes (metaclass of sub-class must itself be a sub-class of the metaclass of its super).
Comment in code indicates this is a deprecation mechanism slated for removal:
# TODO: remove metaclass in 2.1
class FilterMixin(metaclass=FilterMixinRenames):
Would you accept a pull request to remove this metaclass?
thanks.