Is it possible to integrate Keras and TensorFlow code?
A naive approach to integrate Keras and Tensorflow:

input_img = tf.placeholder(tf.float32, (1,200,300,3), name='input_img')
vgg19 = tf.keras.applications.VGG19(weights='imagenet', include_top=False)
output = vgg19(input_img)

with tf.Session() as sess:
    sess.run(tf.global_variables_initializer())
    output_val = sess.run(output, {input_img: 
                          np.expand_dims(img,0)})

output_val.shape, output_val.mean()