title: What type do I use for a Sequence of Strings
body: <p>I want to write a function that accepts an argument that is a Sequence of Strings (not necessarily an array of Strings, but anything that implements the Sequence protocol where the items in the sequence are Strings).</p>
  <p>Actually, I'd like to pass in the keys to a dictionary that is keyed by strings (preferably, without creating a temporary array).</p>
  <p>I can't seem to find the right syntax to specify that type for the argument.</p>