KeyError when testing

[faircreek]

import piera
h = piera.Hiera("DevTro/modules_tro-ipf/hiera/common/dpfprofiles.yaml")
Traceback (most recent call last):
File "", line 1, in
File "/home/jorm/.local/lib/python2.7/site-packages/piera/piera.py", line 80, in init
self.load(backends or [YAMLBackend, JSONBackend])
File "/home/jorm/.local/lib/python2.7/site-packages/piera/piera.py", line 104, in load
for backend in self.base[':backends']:
KeyError: ':backends'