Picks the element at a given position in a list. Returns nothing if the index
is past the end.Sibling of At Date, which picks by date instead of by position.
Index — zero-based position. 0 is the first element, -1 is the
last, -2 is the second-to-last, and so on. Wire the port, or type a
literal in the inspector. A connected port wins over the literal.