Need guidance to use .map,.group,.pluck, etc. to make multi series line chart in ruby on rails app

I'm trying to display a multi series line chart using chartkick in a Ruby on Rails app.

The chart should display paper_types and the weightfor each type during some time period.

SCREENSHOT ADDED

This is my latest try:

<%= line_chart [                            
  {name: @pappi.map{|p| [p.paper_type]}, data: @pappi.map{|t| [t.date, t.paper_weight] }, 'interpolateNulls':true}
 ] %>

Where @pappi = Paper.all

The code above outputs as the picture below, where every paper_type rounds up on one single line, instead of showing separate lines for each paper_type.

What I'm looking for is a chart similar to the screenshot below, were each paper_type has it's own line.

Can someone please help me with this so I can get the outcome I want?