Object[] (PsiElement element) { XmlTag tag = (XmlTag)element.getParent().getParent(); XmlAttribute[] attributes = tag.getAttributes(); final PsiReference[] refs = element.getReferences(); return ContainerUtil.mapNotNull(attributes, attribute -> { final String attributeValue = attribute.getValue(); return attributeValue != null && attribute.isNamespaceDeclaration() && ContainerUtil.find(refs, ref -> ref.getCanonicalText().equals(attributeValue)) == null ? attributeValue + " " : null; }, ArrayUtilRt.EMPTY_OBJECT_ARRAY); }