':param keymaster: a Keymaster instance
:param account: account name
:param container: container name
:param obj: object name'

def __init__(self, keymaster, account, container, obj):

    super(KeyMasterContext, self).__init__(keymaster.app)
    self.keymaster = keymaster
    self.account = account
    self.container = container
    self.obj = obj
    self._keys = None
