code: func lineAttr(pdf *Fpdf, clr RGBAType, lineWd float64) {
  	pdf.SetLineWidth(lineWd)
  	pdf.SetAlpha(clr.Alpha, "Normal")
  	pdf.SetDrawColor(clr.R, clr.G, clr.B)
  }
docs: // func (g *GridType) SetXExtent(dataLf, paperLf, dataRt, paperRt float64) {
  // 	g.xm, g.xb = linear(dataLf, paperLf, dataRt, paperRt)
  // }
  // func (g *GridType) SetYExtent(dataTp, paperTp, dataBt, paperBt float64) {
  // 	g.ym, g.yb = linear(dataTp, paperTp, dataBt, paperBt)
  // }