concat functions take 2 lists as a input and returns a new list
`` ## element `element` function in TF is selects single element from a list.
element(concat(aws_vpc.generic.*.id, [""]), 0)
In above code, we have used `concat` and `element` both with using `element` we are just selecting the value at the 0th index in the list. ## flatten `flatten` function in