Keras get_weights() returning empty

问题:

I am teaching myself data science and something peculiar has caught my eyes. In a sample DNN tutorial I was working on, I found that the Keras layer.get_weights() function returned empty list for my variables. I've successfully cross validated and used model.fit() function to compute the recall scores.

But as I'm trying to use the get_weights() function on my categorical variables, it returns empty weights for all.

I'm not looking for a solution to code but am just curious on what would possibly cause this. I've read through the Keras API but it did not provide me with information I was hoping to see. What could cause the get_weights() function in keras to return empty list except for of course the weights not being set?