Child nodes does not display for angular-tree-component

I tried implementing angular-tree-component from basic example provided => Angular Tree Example

The issue is after implementation i am only able to see only root nodes and that too without expand(child roots are not visible). There is no error as such in console.

Component:

 @Component({
  selector: 'app-category',
  templateUrl: './category.component.html',
  styleUrls: [
    './category.component.css'
  ]
})
export class CategoryComponent implements OnInit {

  nodes: any;
  options = {};
  showpanel: boolean;
  categories: CategoriesModel[];
  constructor(private adminService: AdminService) {

  }
  ngOnInit() {
    this.showpanel = false;
    this.categories = [];
    this.adminService.getCategoryData()
      .subscribe(
        (catData: CategoriesModel[]) => {
          this.categories = catData;
          this.showpanel = true;
        });
        this.nodes =  [
          {
            id: 1,
            name: 'root1',
            children: [
              { id: 2, name: 'child1' },
              { id: 3, name: 'child2' }
            ]
          },
          {
            id: 4,
            name: 'root2',
            children: [
              { id: 5, name: 'child2.1' },
              {
                id: 6,
                name: 'child2.2',
                children: [
                  { id: 7, name: 'subsub' }
                ]
              }
            ]
          }
        ];
  }
}

HTML:

    <div >
  <tree-root [nodes]="nodes" [options]="options"></tree-root>
</div>

CSS:

    .tree-children.tree-children-no-padding { padding-left: 0 }
.tree-children { padding-left: 20px; overflow: hidden }
.node-drop-slot { display: block; height: 2px }
.node-drop-slot.is-dragging-over { background: #ddffee; height: 20px; border: 2px dotted #888; }
.toggle-children-wrapper-expanded .toggle-children { transform: rotate(90deg) }
.toggle-children-wrapper-collapsed .toggle-children { transform: rotate(0); }
.toggle-children-wrapper {
  padding: 2px 3px 5px 1px;
}
.toggle-children-placeholder {
  display: inline-block;
  height: 10px;
  width: 10px;
  position: relative;
  top: 1px;
  padding-right: 3px;
}
.node-content-wrapper {
  display: inline-block;
  padding: 2px 5px;
  border-radius: 2px;
  transition: background-color .15s,box-shadow .15s;
}
.node-wrapper {display: flex; align-items: flex-start;}
.node-content-wrapper-active,
.node-content-wrapper.node-content-wrapper-active:hover,
.node-content-wrapper-active.node-content-wrapper-focused {
  background: #beebff;
}
.node-content-wrapper-focused { background: #e7f4f9 }
.node-content-wrapper:hover { background: #f7fbff }
.node-content-wrapper-active, .node-content-wrapper-focused, .node-content-wrapper:hover {
  box-shadow: inset 0 0 1px #999;
}
.node-content-wrapper.is-dragging-over { background: #ddffee; box-shadow: inset 0 0 1px #999; }
.node-content-wrapper.is-dragging-over-disabled { opacity: 0.5 }

tree-viewport {
  -webkit-tap-highlight-color: transparent;
  height: 100%;
  overflow: auto;
  display: block;
}
.tree-children { padding-left: 20px }
.empty-tree-drop-slot .node-drop-slot { height: 20px; min-width: 100px }
.angular-tree-component {
  width: 100%;
  position:relative;
  display: inline-block;
  cursor: pointer;
  -webkit-touch-callout: none; /* iOS Safari */
  -webkit-user-select: none;   /* Chrome/Safari/Opera */
  -khtml-user-select: none;    /* Konqueror */
  -moz-user-select: none;      /* Firefox */
  -ms-user-select: none;       /* IE/Edge */
  user-select: none;           /* non-prefixed version, currently not supported by any browser */
}

tree-root .angular-tree-component-rtl {
  direction: rtl;
}
tree-root .angular-tree-component-rtl .toggle-children-wrapper-collapsed .toggle-children {
  transform: rotate(180deg) !important;
}
tree-root .angular-tree-component-rtl .tree-children {
  padding-right: 20px;
  padding-left: 0;
}

tree-node-checkbox {
  padding: 1px;
}

Display in Browser: