def __build_payload(self, size, operation=False, startdate=None):
        """Build payload"""

        payload = {
            'ws.size': size,
            'order_by': 'date_last_updated',
            'omit_duplicates': 'false',
            'status': ["New", "Incomplete", "Opinion", "Invalid", "Won't Fix",
                       "Expired", "Confirmed", "Triaged", "In Progress",
                       "Fix Committed", "Fix Released",
                       "Incomplete (with response)",
                       "Incomplete (without response)"]
        }

        if operation:
            payload['ws.op'] = 'searchTasks'
        if startdate:
            startdate = startdate.isoformat()
            payload['modified_since'] = startdate

        return payload