Set the begin timestamp of the linguistic processor, set to None for the current time
        @type btimestamp: string
        @param btimestamp: version of the linguistic processor

def set_beginTimestamp(self,btimestamp=None):
        """
        Set the begin timestamp of the linguistic processor, set to None for the current time
        @type btimestamp: string
        @param btimestamp: version of the linguistic processor
        """
        if btimestamp is None:
            import time
            btimestamp = time.strftime('%Y-%m-%dT%H:%M:%S%Z')
        self.node.set('beginTimestamp',btimestamp)