Calculate the BPS per LAG from the absolute bytes counter from each interface.

SELECT SUM(bps) 
FROM ( 
     SELECT non_negative_derivative(max("input-bytes"), 1s) * 8 as bps 
     FROM  "jnpr_interface_stat" 
     WHERE ("interface" =~ /et/)  AND $timeFilter 
     GROUP BY time($interval), "device", "interface"
 ) 
GROUP BY time($interval), "parent"