Sambamba's view filter tool, used to filter down a BAM to one with reads
matching some predicate (filter language at https://github.com/lomereiter/sambamba/wiki/%5Bsambamba-view%5D-Filter-expression-syntax).
Tag a product of the EDSL as “interesting to be saved” (the meaning is
implementation dependent; when compiling to a Ketrew workflow this means
copying the file(s) to another directory.