ChartHorizontalLine

 using cAlgo.API;
 namespace cAlgo
 {
     // This sample indicator shows how to use Chart.DrawHorizontalLine method to draw an horizontal line
     [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
     public class HorizontalLineSample : Indicator
     {
         protected override void Initialize()
         {
             Chart.DrawHorizontalLine("horizontalLine", Bars.ClosePrices.LastValue, Color.Red);
         }
         public override void Calculate(int index)
         {
         }
     }
 }

 import clr
 clr.AddReference("cAlgo.API")
 from cAlgo.API import *
 class Test():
     def initialize(self):
         api.Chart.DrawHorizontalLine("horizontalLine", api.Bars.ClosePrices.LastValue, Color.Red)