Answer: In TF 2.0 you should use tf.compat.v1.Session() instead of tf.Session() Use the following code to get rid of the error in Tensorflow2.0:
import tensorflow as tf
tf.compat.v1.Session()
i.e. in your code above, replace this line self.sess = tf.compat.v1.keras.backend.get_session()of code with
self.sess = tf.compat.v1.Session()
Reference:
https://github.com/tensorflow/tensorflow/issues/26844#issuecomment-474038678