text: import { fromEvent } from 'rxjs/observable/fromEvent'
  
  export const WindowSources = {
    keyDown$: fromEvent(window, 'keydown'),
    keyUp$: fromEvent(window, 'keyup'),
    blur$: fromEvent(window, 'blur'),
    mouseMove$: fromEvent(window, 'mousemove'),
    mouseDown$: fromEvent(window, 'mousedown')
  }
  