le(xValue(d)))
            .attr('x', 0).attr('y', d => yScale(yValue(d)));
            // adding axes: 
            const xAxisMethod = d3.axisBottom(xScale);
            const yAxisMethod = d3.axisLeft(yScale);
            // xAxisMethod.ticks(20);
            // xAxisMethod.tickSize(-innerHeight)
            const xAxisGroup = mainGroup.append('g').call(xAxisMethod);
            const yAxisGroup = mainGroup.append('g').call(yAxisMethod);
            xAxisGroup.attr('transform', `translate(${0}, ${innerHe