@Override
			protected void onServicesInvalidated() {
				// empty default implementation
			}
This method returns the GATT callback used by the manager.
<p>
Since version 2.6 this method is private. The manager just can implement all inner methods
directly, without additional object.

@return The gatt callback object.
@deprecated Implement all methods directly in your manager.
ble/src/main/java/no/nordicsemi/android/ble/BleManager.java