'Delete the value specified by `kvs_key`.
Arguments:
kvs_key (`DjangoKeyValueStore.Key`): The field value to delete
Raises: KeyError if key isn\'t found in the cache'

@contract(kvs_key=DjangoKeyValueStore.Key)
def delete(self, kvs_key):

    cache_key = self._cache_key_for_kvs_key(kvs_key)
    field_object = self._cache.get(cache_key)
    if (field_object is None):
        raise KeyError(kvs_key.field_name)
    field_object.delete()
    del self._cache[cache_key]
