code: public MobicentsSipApplicationSession removeSipApplicationSession(final MobicentsSipApplicationSessionKey key) {
  		if(logger.isDebugEnabled()) {
  			logger.debug("Removing a sip application session with the key : " + key);
  		}
  		MobicentsSipApplicationSession sipApplicationSession  = sipApplicationSessions.remove(key);
  		if(sipApplicationSession != null) {
  			final String appGeneratedKey = sipApplicationSession.getKey().getAppGeneratedKey();
  			if(appGeneratedKey != null) {
  				sipApplicationSessionsByAppGeneratedKey.remove(appGeneratedKey);
  			}
  		}
  		return sipApplicationSession;
  	}
docs: Removes a sip application session from the manager by its key
  @param key the identifier for this session
  @return the sip application session that had just been removed, null otherwise