update(mPropertyBag) {
			if (mPropertyBag.flexObject.fileType === "variant") {
				mPropertyBag.isLegacyVariant = true;
			}
			mPropertyBag.method = "PUT";
			return _doWrite(mPropertyBag);
		}
Update an existing flex data stored in LRep back end.

@param {object} mPropertyBag Property bag
@param {object} mPropertyBag.flexObject Flex Object to be updated
@param {string} mPropertyBag.url Configured url for the connector
@param {string} [mPropertyBag.transport] The transport ID
@returns {Promise} Resolves as soon as the writing is completed without data