code: def hash_file(filename):
      
      sha256 = hashlib.sha256()
      with open(filename, 'rb') as f:
          for chunk in iter(lambda: f.read(8192), b''):
              sha256.update(chunk)
      return 'sha256:' + sha256.hexdigest()
docs: Hash a file using the same method the registry uses (currently SHA-256).
  
      :param filename: Name of file to hash
      :type filename: str
  
      :rtype: str
      :returns: Hex-encoded hash of file's content (prefixed by ``sha256:``)