Use of num_events_template [legacy]

[iiSeymour]

Hey @roblanf

Events are no longer relevant with modern basecallers and Guppy considers all event fields in the sequence summary as legacy. A cursory look at the code suggests only num_events_template is being used to colour the read length vs. q score scatterplot and I think a switch to template_duration would be suitable?

This is in preparation for adding a summary file output in bonito as I won't be adding any event related fields.

cc @jaquol

[roblanf]

OK - that sounds like a good idea. Will update when it's done.