load() {
				return Promise.reject("versions.load is not implemented");
			}
Interface called to get the flex versions.

@param {object} mPropertyBag Property bag
@param {sap.ui.fl.Layer} mPropertyBag.layer Layer
@param {string} mPropertyBag.reference Flex reference
@returns {Promise<sap.ui.fl.Version[]>} Resolves with an object containing the data for the versions