new_contents: REF= "/home/ubuntu/refs/bwa_index/GCF_000001405.30_GRCh38.p4_genomic.fna"
  BWA="/opt/biobuilds/bin/bwa"
  SAMTOOLS="/opt/biobuilds/bin/samtools"
  FREEBAYES="/home/ubuntu/freebayes/bin/freebayes"
  VCFILTER="/home/ubuntu/vcflib/bin/vcffilter"
  
subject: Create snake_env.py