public Collection getGrantTokens() {
    synchronized (grantTokens) {
      return Collections.unmodifiableCollection(grantTokens.values());
    }
  }
TEST HOOK: Returns an unmodifible collection backed by the values of the DLockGrantToken map
for testing purposes only.
<p>
Synchronizes on grantTokens.

@return unmodifible collection of the grant tokens
geode-core/src/main/java/org/apache/geode/distributed/internal/locks/DLockGrantor.java