code: function (key) {
  				var pHas, oMsr = startMeasurements("has", key);
  				Log.debug("Cache Manager: has key [" + key + "] called");
  
  				pHas = this._callInstanceMethod("has", arguments).then(function callInstanceHandler(result) {
  					oMsr.endAsync();
  					Log.debug("Cache Manager: has key [" + key + "] returned " + result);
  					return result;
  				});
  				oMsr.endSync();
  				return pHas;
  			}
docs: Checks whether certain entry exists.
  @param {string|number} key the key to look for. Null is not accepted.
  @returns {Promise} a promise that would be resolved in case of successful operation or rejected with
  value of the error message if the operation fails. It resolves with a boolean value of true - if an entry
  with the given key is found, false - otherwise
  @public