code: public void logout( String token ) {
  		if( token != null ) {
  			this.tokenToLoginTime.remove( token );
  			this.tokenToUsername.remove( token );
  		}
  	}
docs: Invalidates a session.
  <p>
  No error is thrown if the session was already invalid.
  </p>
  
  @param token a token (can be null)