Is there a trick to using this in a "playground"

[ddownn]

I have put the SwiftDate package in Sources (also tried it in Resources) in a playground, but when I try
import SwiftDate
print("2021-01-14T14:36:17+00:00".toISODate()!)
I just get
error: value of type 'String' has no member 'toISODate'