That error message shows that your defined line is not named trix, hence the error.
Or else you mean the strategy's next in which you obviously have to go over the variable in which you have stored the reference to the indicator.
I have MyTric.py and stretegy with imported MyTrix. Now I want to use self.lines.trix in this strategy. How can i do it? This line plot's on figure, but I don't understend how to get it's values.