from collections import namedtuple

class CacheKey(namedtuple('CacheKey', ['key', 'expiration'])):
  """ Defines a key into the data model cache. """
  pass

def for_repository_blob(namespace_name, repo_name, digest):
  return CacheKey('repository_blob__%s_%s_%s' % (namespace_name, repo_name, digest), '60s')