1.  ng-zorro   nz-submenu  get the child  nz-submenu  through  @ ContentChildren ()  and set its  level  property to realize the left offset of the child  nz-submenu  in the menu tree; 
  
 
 2. Use  nz-submenu  to make a dynamic menu. You need to create a new build and recursive. 
 the problem encountered now is:  @ ContentChildren ()  seems to only grab the child  nz-submenu  within the component, but cannot get the child  nz-submenu  in the recursion, so the  level  of the child  nz-submenu  cannot be set in the recursion, which leads to the left alignment of the child  nz-submenu  with the parent  nz-submenu , which can not achieve the display effect. 
 my solution is to set the  level  property, but it has no @ Input () decoration and cannot be set from external components; 
 do you have any solutions? 
