code: def dnld_assc(assc_name, go2obj=None, prt=sys.stdout):
      
      # Example assc_name: "tair.gaf"
      # Download the Association
      dirloc, assc_base = os.path.split(assc_name)
      if not dirloc:
          dirloc = os.getcwd()
      assc_locfile = os.path.join(dirloc, assc_base) if not dirloc else assc_name
      dnld_annotation(assc_locfile, prt)
      # Read the downloaded association
      assc_orig = read_gaf(assc_locfile, prt)
      if go2obj is None:
          return assc_orig
      # If a GO DAG is provided, use only GO IDs present in the GO DAG
      assc = {}
      goids_dag = set(go2obj.keys())
      for gene, goids_cur in assc_orig.items():
          assc[gene] = goids_cur.intersection(goids_dag)
      return assc
docs: Download association from http://geneontology.org/gene-associations.