Bug 145991 [Regression]Invalid data set should not be allowed to drag or "Insert in layout"
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DataSetHandle.java
{
		return getStringProperty( SimpleDataSet.ON_FETCH_METHOD );
	}
	/**
	 * Sets the code for the onFetch method. This is the script called just
	 * after fetching each row.
	 * 
	 * @param code
	 *            the code for the method
	 * @throws SemanticException
	 *             If the method is locked.
	 */
	public void setOnFetch( String code ) throws SemanticException
	{
		setProperty( SimpleDataSet.ON_FETCH_METHOD, code );
	}
	/**
	 * Return a handle to deal with the cached data set information that include
	 * output column information when it gets from databases, input/output
	 * parameter definitions.
	 * 
	 * @return a <code>CachedMetaDataHandle</code> to deal with the cached
	 *         data set information, return <code>null</code> if the property
	 *         has not been set.
	 */
	public CachedMetaDataHandle getCachedMetaDataHandle( )
	{
		PropertyHandle propHandle = this
				.getPropertyHandle( SimpleDataSet.CACHED_METADATA_PROP );
		assert propHandle != null;