code: def checkfiles(args):
    
  
    from .query import Database
    db = Database()
  
    r = db.objects()
  
    # go through all files, check if they are available on the filesystem
    good = []
    bad = []
    for f in r:
      if os.path.exists(f.make_path(args.directory, args.extension)):
        good.append(f)
      else:
        bad.append(f)
  
    # report
    output = sys.stdout
    if args.selftest:
      from bob.db.utils import null
      output = null()
  
    if bad:
      for f in bad:
        output.write('Cannot find file "%s"\n' % (f.make_path(args.directory, args.extension),))
      output.write('%d files (out of %d) were not found at "%s"\n' % \
        (len(bad), len(r), args.directory))
  
    return 0
docs: Checks existence of files based on your criteria