Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/ExtendsCommand.java
import org.eclipse.birt.report.model.api.elements.ReportDesignConstants;
import org.eclipse.birt.report.model.api.metadata.IElementDefn;
import org.eclipse.birt.report.model.api.metadata.PropertyValueException;
import org.eclipse.birt.report.model.api.util.StringUtil;
import org.eclipse.birt.report.model.core.CachedMemberRef;
import org.eclipse.birt.report.model.core.DesignElement;
import org.eclipse.birt.report.model.core.Module;
import org.eclipse.birt.report.model.core.StyledElement;
import org.eclipse.birt.report.model.elements.Library;
import org.eclipse.birt.report.model.elements.interfaces.IDesignElementModel;
import org.eclipse.birt.report.model.metadata.ElementDefn;
import org.eclipse.birt.report.model.metadata.ElementPropertyDefn;
import org.eclipse.birt.report.model.metadata.ElementRefValue;
import org.eclipse.birt.report.model.metadata.MetaDataDictionary;
import org.eclipse.birt.report.model.metadata.PropertyDefn;
import org.eclipse.birt.report.model.metadata.PropertyType;
import org.eclipse.birt.report.model.util.ContentIterator;
import org.eclipse.birt.report.model.util.ModelUtil;
import org.eclipse.birt.report.model.util.ReferenceValueUtil;
/**
 * Sets the "extends" attribute of an element.
 * 
 */
public class ExtendsCommand extends AbstractElementCommand
{
	/**
	 * Constructor.
	 * 
	 * @param module
	 *            the module