containsXY(x, y) {
    const flatCoordinates = this.flatCoordinates;
    const dx = x - flatCoordinates[0];
    const dy = y - flatCoordinates[1];
    return dx * dx + dy * dy <= this.getRadiusSquared_();
  }
@param {number} x X.
@param {number} y Y.
@return {boolean} Contains (x, y).
@override