KeyError: <built-in function format> in SepNMF

[cympfh]

I'm using Python 3.6.8 and tried SepNMF. (I know that this is tested not on 3.6.8)
Then I got KeyError: <built-in function format> by following code:

import nimfa

model = nimfa.SepNmf(X_uw)  # lil_matrix
model.factorize()

I have checked the code and I wonder theformat variable not defined? (of course, format is build-in in Python 3.x). Is this a bug of SepNMF?

https://github.com/marinkaz/nimfa/blob/master/nimfa/methods/factorization/sepnmf.py#L300

[LauraRichter]

I'm having the same problem