Circle in CZML

Is it possible to create a circle shape by loading a CZML file?

I've found an old post that states "Both circles and ellipses are now supported directly in CZML", but found no documentation on that matter.

I tried something like this, but it didn't work:

"circle": {
  "center": center,
  "radius": radius,
  "material": {
    "solidColor": {
      "color": {
        "rgba": color
      }
    }
  }
}

If circle is supported, could someone provide an example?

A circle is an ellipse where the semi-major and semi-minor axes are the same - which is then the radius.

Worked like a charm! Thank you.