Reads strain names from one or more plain text files and returns the
set of distinct strains.
Strain names can be commented with full-line or inline comments. For
example, the following is a valid strain names file:
# this is a comment at the top of the filestrain1# exclude strain1 because it isn't sequenced properlystrain2# this is an empty line that will be ignored.
Parameters:
files (iterable of str) – one or more names of text files with one strain name per line