How to use linear_trend?

[gloryVine]

I find the documentation of tsfresh.feature_extraction.feature_calculators.linear_trend to be lacking. Specifically, I do not understand

'param (list) – contains dictionaries {“attr”: x} with x an string, the attribute name of the regression model'

What is meant by this? Let's say I have a time series x=[1,2,3,4,5], then what do I have to pass as param?