function Cesium3DContentGroup(options) {
  options = options ?? Frozen.EMPTY_OBJECT;
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("options.metadata", options.metadata);
  //>>includeEnd('debug');

  this._metadata = options.metadata;
}
Simple abstraction for a group. This class exists to make the metadata API
more consistent, i.e. metadata can be accessed via
<code>content.group.metadata</code> much like tile metadata is accessed as
<code>tile.metadata</code>.

@param {object} options Object with the following properties:
@param {GroupMetadata} options.metadata The metadata associated with this group.

@alias Cesium3DContentGroup
@constructor
@private
@experimental This feature is using part of the 3D Tiles spec that is not final and is subject to change without Cesium's standard deprecation policy.