Process the start of the top-level xtvd node

def _startXTVDNode(self, name, attrs):
        """Process the start of the top-level xtvd node"""

        schemaVersion = attrs.get('schemaVersion')
        validFrom = self._parseDateTime(attrs.get('from'))
        validTo = self._parseDateTime(attrs.get('to'))
        self._progress.printMsg('Parsing version %s data from %s to %s' %
                                    (schemaVersion,
                                     validFrom.strftime('%Y/%m/%d'),
                                     validTo.strftime('%Y/%m/%d')))