
    <nz-select [(ngModel)]="selectedValue" nzAllowClear nzPlaceHolder="Choose" nzShowSearch>
      <nz-option-group nzLabel="Manager">
        <nz-option nzValue="jack" nzLabel="Jack"></nz-option>
        <nz-option nzValue="lucy" nzLabel="Lucy"></nz-option>
      </nz-option-group>
      <nz-option-group nzLabel="Engineer">
        <nz-option nzValue="tom" nzLabel="Tom"></nz-option>
      </nz-option-group>
    </nz-select>
  