def _sincedb_start_position(self):
        """Retrieves the starting position from the sincedb sql db
        for a given file
        """
        if not self._sincedb_path:
            return None

        self._sincedb_init()
        self._log_debug('retrieving start_position from sincedb')
        conn = sqlite3.connect(self._sincedb_path, isolation_level=None)
        cursor = conn.cursor()
        cursor.execute('select position from sincedb where fid = :fid and filename = :filename', {
            'fid': self._fid,
            'filename': self._filename
        })

        start_position = None
        for row in cursor.fetchall():
            start_position, = row

        return start_position
Retrieves the starting position from the sincedb sql db
        for a given file