ore than once, each subscription
will individually call <code>convert</code> on each data event.</p>
<p>Unlike <a href="dart-async/Stream/transform.html">transform</a>, this method does not treat the stream as
chunks of a single value. Instead each event is converted independently
of the previous and following events, which may not always be correct.
For example, UTF-8 encoding, or decoding, will give wrong results
if a surrogate pair, or a multibyte UTF-8 encoding, is split into
separate events, and those 