docs: @SuppressWarnings("unchecked")
      private Collection<String> evalForCollection(String attributeName)
      {
          Object value = getStateHelper().eval(attributeName);
          if (value == null)
          {
              return Collections.<String>emptyList();
          }
          else if (value instanceof Collection)
          {
              return (Collection<String>) value;
          }
          else if (value instanceof String)
          {
              return getCollectionFromSpaceSplitString((String) value);
          }
          else
          {
              throw new IllegalArgumentException("Type " + value.getClass()
                      + " not supported for attribute " + attributeName);
          }
      }