getLines method
Implementation
List<List<Line>> getLines() {
var xlines =
getLinesParallelToAxis(xAxis, yAxis, xLineFrequency, fadedLineRatio);
var ylines =
getLinesParallelToAxis(yAxis, xAxis, yLineFrequency, fadedLineRatio);
var lines1 = [...xlines[0], ...ylines[0]];
var lines2 = [...xlines[1], ...ylines[1]];
return [lines1, lines2];
}