type parentObj = object of RootObj

type
    childObj1 = object of parentOBj
    childObj2 = object of parentOBj

method whine(self: parentObj) =
    echo "Shutup!"

method whine(self: childObj1) =
    echo "But.... mooooooooooooooooom"

method whine(self: childObj2) =
    echo "But.... daaaaaaaaaaaaaaaaad"

var myseq: seq[parentObj] = @[]

myseq.add(childObj1())
myseq.add(childObj2())

for obj in myseq:
    obj.whine()