fix

adapters/saml/as7-eap6/subsystem/src/main/java/org/keycloak/subsystem/saml/as7/KeycloakSubsystemParser.java

@@ -33,6 +33,7 @@ import org.jboss.staxmapper.XMLExtendedStreamWriter;
 import javax.xml.stream.XMLStreamConstants;
 import javax.xml.stream.XMLStreamException;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Set;