Fixed incorrect isinstance check in plotting.widgets
Fixed incorrect isinstance check in plotting.widgets

ioam/holoviews,vascotenner/holoviews,basnijholt/holoviews,ioam/holoviews,basnijholt/holoviews,vascotenner/holoviews,basnijholt/holoviews,vascotenner/holoviews,ioam/holoviews