Fix also __slots__ to ensure proper unpickling
Fix also __slots__ to ensure proper unpickling

mloesch/tablib,godfreyy/tablib,durden/tablib,zhengzhihust/tablib,alex/tablib,screwt/tablib,leohmoraes/tablib,bopo/tablib,whix/tablib,tommyanthony/tablib,bopo/tablib,steveb/tablib,enzochiau/tablib,whix/tablib,klothe/tablib,enzochiau/tablib,zhengzhihust/tablib,steveb/tablib,godfreyy/tablib,klothe/tablib,screwt/tablib,kennethreitz/tablib,leohmoraes/tablib,mloesch/tablib