Custom visual Legend is not filtering data

Hi All,

the below custom visual is "Multiple Axes chart - xViz". This worked perfectly for my requirement. 

The only problem that i have been facing is, the legend. in any visual, when we click on particular item in legend that filters the data for that chart and for other charts as well. 

But this custom visual, is excluding the particular item selected and showing values for years.

For example : 

in any visual - when i click on 2020 in the legend, the behaviour we expect is to show/highligh line chart for 2020

in this custom visual - when i click on 2020 in the legend, it excludes 2020 and show 2019 & 2018 lines. like in the 2nd pic below.

Any idea how i can get this work? please help