a (possibly lazy) list of completion example strings. These strings are continuations of user's input. The user's input is incremented with calls to withAddedPrefix.
the examples that will be displayed to the user when they press the TAB key.
a string that just typed in by the user.
a new source of only those examples that start with the string typed by the user so far (with addition of the just added prefix).
A convenience example source that wraps any collection of strings into a source of examples.
the examples that will be displayed to the user when they press the TAB key.