Fixed the flask8 error in load / dump only documentation
Fixed the flask8 error in load / dump only documentation

xLegoz/marshmallow,quxiaolong1504/marshmallow,bartaelterman/marshmallow,mwstobo/marshmallow,Bachmann1234/marshmallow,etataurov/marshmallow,Tim-Erwin/marshmallow,VladimirPal/marshmallow,dwieeb/marshmallow,daniloakamine/marshmallow,maximkulkin/marshmallow,marshmallow-code/marshmallow