code: public void insert(final int index, final Object item) {
          if (mAnimateAdditionAdapter == null) {
              throw new IllegalStateException("Adapter should implement Insertable!");
          }
          mAnimateAdditionAdapter.insert(index, item);
      }
docs: Inserts an item at given index. Will show an entrance animation for the new item if the newly added item is visible.
  Will also call {@link Insertable#add(int, Object)} of the root {@link android.widget.BaseAdapter}.
  
  @param index the index the new item should be inserted at.
  @param item  the item to insert.
  
  @throws java.lang.IllegalStateException if the adapter that was set does not implement {@link com.nhaarman.listviewanimations.util.Insertable}.