code: def do_verify(marfile, keyfiles=None):
      
      try:
          with open(marfile, 'rb') as f:
              with MarReader(f) as m:
                  # Check various parts of the mar file
                  # e.g. signature algorithms and additional block sections
                  errors = m.get_errors()
                  if errors:
                      print("File is not well formed: {}".format(errors))
                      sys.exit(1)
  
                  if keyfiles:
                      try:
                          keys = get_keys(keyfiles, m.signature_type)
                      except ValueError as e:
                          print(e)
                          sys.exit(1)
  
                      if any(m.verify(key) for key in keys):
                          print("Verification OK")
                          return True
                      else:
                          print("Verification failed")
                          sys.exit(1)
                  else:
                      print("Verification OK")
                      return True
  
      except Exception as e:
          print("Error opening or parsing file: {}".format(e))
          sys.exit(1)
docs: Verify the MAR file.