work around contravariant function type issue
work around contravariant function type issue

jdetle/nteract,captainsafia/nteract,rgbkrk/nteract,nteract/nteract,jdfreder/nteract,nteract/composition,jdfreder/nteract,nteract/composition,rgbkrk/nteract,captainsafia/nteract,jdetle/nteract,jdetle/nteract,rgbkrk/nteract,captainsafia/nteract,nteract/nteract,jdetle/nteract,rgbkrk/nteract,jdfreder/nteract,nteract/nteract,nteract/nteract,nteract/nteract,rgbkrk/nteract,jdfreder/nteract,captainsafia/nteract,nteract/composition