code: protected final ServiceTracker<T, W> create(String filter) {
  		try {
  			return new ServiceTracker<>(bundleContext, bundleContext.createFilter(filter), this);
  		} catch (InvalidSyntaxException e) {
  			throw new IllegalArgumentException("Unexpected InvalidSyntaxException: " + e.getMessage());
  		}
  	}
docs: Creates a new tracker that tracks services by generic filter
  
  @param filter generic filter to use for tracker
  @return a configured osgi service tracker