code: def connectdown(np, p, acc, outlet, wtsd=None, workingdir=None, mpiexedir=None,
                      exedir=None, log_file=None, runtime_file=None, hostfile=None):
          
          # If watershed is not specified, use acc to generate a mask layer.
          if wtsd is None or not os.path.isfile(wtsd):
              p, workingdir = TauDEM.check_infile_and_wp(p, workingdir)
              wtsd = workingdir + os.sep + 'wtsd_default.tif'
              RasterUtilClass.get_mask_from_raster(p, wtsd, True)
          fname = TauDEM.func_name('connectdown')
          return TauDEM.run(FileClass.get_executable_fullpath(fname, exedir),
                            {'-p': p, '-ad8': acc, '-w': wtsd},
                            workingdir,
                            None,
                            {'-o': outlet},
                            {'mpipath': mpiexedir, 'hostfile': hostfile, 'n': np},
                            {'logfile': log_file, 'runtimefile': runtime_file})
docs: Reads an ad8 contributing area file,
          identifies the location of the largest ad8 value as the outlet of the largest watershed