code: def check_args(args):
      
      check_args_has_attributes(args)
      if args.v:
          non_version_attrs = [v for k, v in args.__dict__.items() if k != 'v']
          print('non_version_attrs', non_version_attrs)
          if len([v for v in non_version_attrs if v is not None]) != 0:
              fail('Cannot show the version number with another command.')
          return
      if args.i is None:
          fail('Cannot draw ER diagram of no database.')
      if args.o is None:
          fail('Cannot draw ER diagram with no output file.')
docs: Checks that the args are coherent.