code: def get_vts_xml(self, vt_id=None, filtered_vts=None):
          
  
          vts_xml = Element('vts')
  
          if vt_id:
              vts_xml.append(self.get_vt_xml(vt_id))
          elif filtered_vts:
              for vt_id in filtered_vts:
                  vts_xml.append(self.get_vt_xml(vt_id))
          else:
              for vt_id in self.vts:
                  vts_xml.append(self.get_vt_xml(vt_id))
  
          return vts_xml
docs: Gets collection of vulnerability test information in XML format.
          If vt_id is specified, the collection will contain only this vt, if
          found.
          If no vt_id is specified, the collection will contain all vts or those
          passed in filtered_vts.
  
          Arguments:
              vt_id (vt_id, optional): ID of the vt to get.
              filtered_vts (dict, optional): Filtered VTs collection.
  
          Return:
              String of collection of vulnerability test information in
              XML format.