Bug 141192 [Viewers] Javadoc change about multiple equal elements in StructuredViewer and AbstractTreeViewer
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* </p>
     * 
     * @param level
     *           non-negative level, or <code>ALL_LEVELS</code> to expand all
     *           levels of the tree
     */
    public void setAutoExpandLevel(int level) {
        expandToLevel = level;
    }
    /**
     * The <code>AbstractTreeViewer</code> implementation of this method
     * checks to ensure that the content provider is an <code>ITreeContentProvider</code>.
     */
    public void setContentProvider(IContentProvider provider) {
    	
        super.setContentProvider(provider);
    }
    
	protected void assertContentProviderType(IContentProvider provider) {
		Assert.isTrue(provider instanceof ITreeContentProvider || provider instanceof ITreePathContentProvider);
	}
    /**
     * Sets the expand state of the given item.
     * 
     * @param item
     *           the item
     * @param expand
     *           the expand state of the item
     */
    protected abstract void setExpanded(Item item, boolean expand);