ImportError: cannot import name 'keras_ctcmodel' from 'keras'

Question

I'm trying to run a Connectionist Temporal Classification Model (Automatic Speech Recognition), and below is the beginning code I got from the example.py in https://github.com/cyprienruffino/CTCModel/blob/master/example.py:

import os
!pip install keras
import keras
!pip install tensorflow
import tensorflow
from keras.layers import TimeDistributed, Activation, Dense, Input, Bidirectional, LSTM, Masking, GaussianNoise
from tensorflow.keras.optimizers import Adam
from keras import keras_ctcmodel
from keras_ctcmodel.CTCModel import CTCModel as CTCModel
import pickle
from keras.preprocessing import sequence
from tensorflow.python.keras.utils.generic_utils import Progbar
import numpy as np
from six.moves.urllib.request import urlretrieve

However, I keep getting an import error on

from keras_ctcmodel.CTCModel import CTCModel as CTCModel

I faced this issue with importing Adam as well until I added tensorflow. Is this a bug in Keras?