input: Write a python function to convert tile coordinates (xt, yt, zoomt) to Google Mercator coordinates.
  assert getTileRect(1, 1, 1) == (-10018754.17, 0.0, 0.0, 10018754.17)
  assert getTileRect(2, 2, 2) == (-10018754.17, -10018754.17, 0.0, 0.0)
  assert getTileRect(0, 0, 0) == (-20037508.34, 20037508.34, -10018754.17, 10018754.17)
output: def getTileRect(xt, yt, zoomt):
      tileSize = 256
      initialResolution = 2 * 20037508.34 / tileSize
      originShift = 20037508.34
  
      def resolution(zoom):
          return initialResolution / (2**zoom)
  
      res = resolution(zoomt)
      minx = xt * tileSize * res - originShift
      maxx = (xt + 1) * tileSize * res - originShift
      miny = -(yt + 1) * tileSize * res + originShift
      maxy = -yt * tileSize * res + originShift
  
      return (minx, miny, maxx, maxy)