AttributeError: module 'tensorflow' has no attribute 'get_default_graph'
Change
Import keras.<something>.<something>
to
Import tensorflow.keras.<something>.<something>
where "something" refers to the module you want to import. It worked for me.
Another cause due to which this is happening is that in tensorflow_backend.py
located in : lib/python3.6/site-packages/keras/backend/
uses tf.compat.v1.get_default_graph for obtaining graph
instead of tf.get_default_graph.
By replacing this in the directory this problem can be solved successfully.