These are lessons 19 & 20

A smaller tool can have a small Docker container and would be more easily used & tested

For "Custom Types", we could use https://github.com/EBI-Metagenomics/ebi-metagenomics-cwl/blob/master/tools/biom-convert.cwl

For "Specifying Software Requirements" we could use https://github.com/EBI-Metagenomics/ebi-metagenomics-cwl/blob/master/tools/nhmmer.cwl

Thanks to @tom-tan for reporting this: #61 (comment)