code: def File(name, dbm_module=None):
      
      global ForDirectory, DB_Name, DB_Module
      if name is None:
          ForDirectory = DirFile
          DB_Module = None
      else:
          ForDirectory = DB
          DB_Name = name
          if not dbm_module is None:
              DB_Module = dbm_module
docs: Arrange for all signatures to be stored in a global .sconsign.db*
      file.