code: function() {
  			if (this._oSortExpression == null) {
  				var oEntityType = this._oParameter.getContainingParameterization().getEntityType();
  				this._oSortExpression = new odata4analytics.SortExpression(oEntityType.getModel(), oEntityType.getSchema(),
  						oEntityType);
  			}
  			return this._oSortExpression;
  		}
docs: Get the sort expression for this request.
  
  Expressions are represented by separate objects. If none exists so far, a
  new expression object gets created.
  
  @returns {sap.ui.model.analytics.odata4analytics.SortExpression} The sort object
  associated to this request.
  @public
  @function
  @name sap.ui.model.analytics.odata4analytics.ParameterValueSetRequest#getSortExpression