code: def dnld_gafs(species_list, prt=sys.stdout, loading_bar=True):
      
      # Example GAF files in  http://current.geneontology.org/annotations/:
      #   http://current.geneontology.org/annotations/mgi.gaf.gz
      #   http://current.geneontology.org/annotations/fb.gaf.gz
      #   http://current.geneontology.org/annotations/goa_human.gaf.gz
      http = "http://current.geneontology.org/annotations"
      # There are two filename patterns for gene associations on geneontology.org
      fin_gafs = []
      cwd = os.getcwd()
      for species_txt in species_list: # e.g., goa_human mgi fb
          gaf_base = '{ABC}.gaf'.format(ABC=species_txt) # goa_human.gaf
          gaf_cwd = os.path.join(cwd, gaf_base) # {CWD}/goa_human.gaf
          wget_cmd = "{HTTP}/{GAF}.gz".format(HTTP=http, GAF=gaf_base)
          dnld_file(wget_cmd, gaf_cwd, prt, loading_bar)
          fin_gafs.append(gaf_cwd)
      return fin_gafs
docs: Download GAF files if necessary.