getUID( attribute, isRelativeCopy = false ) {

		if ( this.uids.has( attribute ) === false ) {

			const uids = new Map();

			uids.set( true, this.uid ++ );
			uids.set( false, this.uid ++ );

			this.uids.set( attribute, uids );

		}

		const uids = this.uids.get( attribute );

		return uids.get( isRelativeCopy );

	}
Returns ids for buffer attributes.

@param {Object} attribute
@param {boolean} [isRelativeCopy=false]
@return {number} An integer