Prediction by Bayesian linear regression

Thank you @cluhmann @OriolAbril for your answers. I really appreciate it.

Now, I want to predict the DV with the following code but I get an error:

bayes_prediction = linear_trace['Intercept'] + linear_trace['slope'] * [16,31,35]

[16,31,35] are three random numbers for slope [0], slope [1] and slope [2].
I don’t know how to put three slopes together to get the prediction. I would like to put my X_test values for my 3 IVs.

I appreciate it if you could help me with this as well.

Thank you.