all currently cached AccessibleProviders.
This method guarantees not to returns null, but an empty list, if no
AccessibleProvider is currrenty cached.
Call {@link #synchronize()} immediately before this method, to
get a result that reflects the most actual state of PanckouckeStore.
org.tm4j.tmnav.env.TMNavProviderManager .getAccessibleProviders()
Returns
Meta Data (1)