code: func PopAttributes() {
  	if len(canvas.attrStack) == 0 {
  		return
  	}
  	a := canvas.attrStack[len(canvas.attrStack)-1]
  	canvas.attrStack = canvas.attrStack[:len(canvas.attrStack)-1]
  	SetTextColor(a.text)
  	SetBackColor(a.back)
  }
docs: // PopAttributes restores saved with PushAttributes colors. Function does
  // nothing if there is no saved colors