code: @RestrictTo(LIBRARY)
    public String url() {
      StringBuilder sb = new StringBuilder();
  
      sb.append("path");
      if (strokeWidth() != null) {
        sb.append("-").append(strokeWidth());
      }
      if (strokeColor() != null) {
        sb.append("+").append(strokeColor());
      }
      if (strokeOpacity() != null) {
        sb.append("-").append(strokeOpacity());
      }
      if (fillColor() != null) {
        sb.append("+").append(fillColor());
      }
      if (fillOpacity() != null) {
        sb.append("-").append(fillOpacity());
      }
      sb.append("(").append(polyline()).append(")");
      return sb.toString();
    }
docs: <em>Used Internally.</em>
  
  @return a String representing the marker part of the URL.
  @since 2.1.0