error: loading model for detruecaser

[colingair]

mtr = MosesTruecaser('big.truecasemodel')

The above is fine. But how to load the same model for detruecasing? It gives error, if I do the following:

from sacremoses import MosesDetruecaser
mdtr = MosesDetruecaser("mymodel_")
Traceback (most recent call last):
File "", line 1, in
TypeError: init() takes 1 positional argument but 2 were given

any suggestion?
Thanks