Example query_df for use in generating a
metagenomeAnnotation-class object using the annotateMgDb-class method. The dataset contains the msd16s OTU ids and
Greengenes database version 13.5 ids. Specifically, the OTU centers came from
'Healthy and moderate to severe diarrhea 16S expression data' - bioconductor
dataset 'msd16s'.