_getNodeRef( cache, index, object ) {

		if ( cache.refs[ index ] <= 1 ) return object;

		const ref = object.clone();

		// Propagates mappings to the cloned object, prevents mappings on the
		// original object from being lost.
		const updateMappings = ( original, clone ) => {

			const mappings = this.associations.get( original );
			if ( mappings != null ) {

				this.associations.set( clone, mappings );

			}

			for ( const [ i, child ] of original.children.entries() ) {

				updateMappings( child, clone.children[ i ] );

			}

		};

		updateMappings( object, ref );

		ref.name += '_instance_' + ( cache.uses[ index ] ++ );

		return ref;

	}
Returns a reference to a shared resource, cloning it if necessary.

@private
@param {Object} cache
@param {number} index
@param {Object} object
@return {Object}