code: @Override
      public Fragment getItem(int position) {
          Fragment f = createItem(position);
          // We should cache fragments manually to access to them later
          mPages.put(position, f);
          return f;
      }
docs: Get a new Fragment instance.
  <p>Each fragments are automatically cached in this method,
  so you don't have to do it by yourself.
  If you want to implement instantiation of Fragments,
  you should override {@link #createItem(int)} instead.</p>
  <p/>
  {@inheritDoc}
  
  @param position Position of the item in the adapter.
  @return Fragment instance.