How can I see the predictor function that Mathematica produces?

I am trying some basic machine learning with Mathematica. I am wondering if I can see the function that Mathematica produces for a training set. I give the following example:

trainingset = {1 -> 1.3, 2 -> 2.4, 3 -> 4.4, 4 -> 5.1, 6 -> 7.3}; p = Predict[trainingset, Method -> "LinearRegression"]

If I type p[1.5], it will give me the predicted value. However, could I also see/know somehow the function used, e.g. for this case in the form of y=a*x+b, (where x is the variable)? Is there a way to see the predicted function?

It turns out that PredictorFunctions are implemented in a nice and transparent way as PredictorFunction[ Association[...]]. So execute p[[1]] and everything is laid out nicely for you.
• Well, the actual predictor consists of one or more neural nets with pre- and postprocessors. Very complicated. You can try to inspect trace = Trace[p[1.5]]; in order to guess what is going on... The working of FindFit or LinearModelFit might be easier to graps. – Henrik Schumacher Jun 19 '18 at 11:40