ViewImage and ViewImageAnnotation do not draw when followed by Prefetch/BuildBatch

[maet3608]

for instance, this does not work (but should) load_images >> ViewImage() >> Prefetch() >> Consume()

The following works: load_images >> Prefetch() >> ViewImage() >> Consume

Similarly the moment a BuildBatch() appears somewhere after ViewImage() drawing does not work because BuildBatch internally uses the same code as Prefetch(). This is threading issue due to the fact that matplotlib is not thread safe.