WIP add cleanUp method.

org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/cli/services/PassiveExpiringSessionCache.java

@@ -118,6 +118,11 @@ public class PassiveExpiringSessionCache implements SessionCache {
     return cachedSessions.keySet();
   }
 
+  @Override
+  public void cleanUp() {
+    removeExpiredSessions();
+  }
+
   /**
    * Session ids generated internally are UUID {@link String}.
    * @return A new {@link String} session id.

org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/cli/services/SessionCache.java

@@ -43,5 +43,10 @@ public interface SessionCache {
    * @return {@link Set} of session ids.
    */
   Set<String> getSessionIds();
-    
+
+  /**
+   * Performs any pending maintenance operations needed by the cache.
+   * */
+  public void cleanUp();
+
 }