def extend(self, items):
<EOL>for item in items:<EOL><INDENT>self.add(item)<EOL><DEDENT>
Add a sequence of items to the work queue.

:param items: A sequence of items to add to the queue.  An
              item may be of any type; however, if they are
              not hashable, then the work queue must either be
              initialized with ``unique`` set to ``False``, or
              a ``key`` callable must have been provided.