'Returns a \'peek\' at the data.'

@web.expose
def peek(self, trans, id=None):

    data = trans.sa_session.query(self.app.model.HistoryDatasetAssociation).get(id)
    if data:
        (yield '<html><body><pre>')
        (yield data.peek)
        (yield '</pre></body></html>')
    else:
        (yield ('No    data    with    id=%d' % id))
