code: private void initAttribute(Object pAttrval) {
          if (pAttrval instanceof String) {
              attributeNames = EscapeUtil.split((String) pAttrval,EscapeUtil.CSV_ESCAPE,",");
              multiAttributeMode = attributeNames.size() > 1;
          } else if (pAttrval instanceof Collection) {
              Collection<String> attributes = (Collection<String>) pAttrval;
              if (attributes.size() == 1 && attributes.iterator().next() == null) {
                  attributeNames = null;
                  multiAttributeMode = false;
              } else {
                  attributeNames = new ArrayList<String>(attributes);
                  multiAttributeMode = true;
              }
          } else if (pAttrval == null) {
              attributeNames = null;
              multiAttributeMode = false;
          } else {
              throw new IllegalArgumentException("Attribute names must be either a String, Collection or null (and not " + pAttrval.getClass() + ")");
          }
      }
docs: initialize and detect multi attribute mode