code: function () {
          var compo = $singleton (Component, {
                          somthingHappened: $triggerOnce () })
  
          $assertEveryCalled (function (first, second) {
              compo.somthingHappened (function (what) { $assert (what, 'somthin'); first () })
              compo.somthingHappened (function (what) { $assert (what, 'somthin'); second () })
              compo.somthingHappened ('somthin') }) }
docs: /*  A variation of trigger. On 'write' operation, it flushes wait queue, so
  no callback bound previously gets called in future (until explicitly
  queued again by 'read' operation).