ImportError: cannot import name 'BCELossMasked'

TTS (Text-to-Speech)
#1

I followed the instruction given at https://github.com/mozilla/TTS and https://gist.github.com/erogol/97516ad65b44dbddb8cd694953187c5b

I can use the pre-trained models, but when I try to train a model following the exact steps of the latter link, I get an error of

python train.py --config_path config.json | tee training.log
Traceback (most recent call last):
  File "train.py", line 16, in <module>
    from TTS.layers.losses import L1LossMasked, MSELossMasked, BCELossMasked
ImportError: cannot import name 'BCELossMasked'

I’m on a Ubuntu 18.04 machine.