code: def _draw_circle(data, obj, draw_options):
      
      x, y = obj.center
      ff = data["float format"]
      cont = ("\\draw[{}] (axis cs:" + ff + "," + ff + ") circle (" + ff + ");\n").format(
          ",".join(draw_options), x, y, obj.get_radius()
      )
      return data, cont
docs: Return the PGFPlots code for circles.