checkbox doesn't work in ng2-smart-table

To add checkbox inside ng2-smart-table, I added the following code. But I found this checkbox inside ng2-smart-table cannot be clicked or changed to checked. If I put it outside of the ng2-smart-table, it can be clicked or changed to checked. What's wrong?

`import { DomSanitizer } from '@angular/platform-browser';`
...
`constructor(private _sanitizer: DomSanitizer) { }`
...
`public settings = {`
` columns: {`
` checkbox: {`
` title: 'Check Box',`
` type: 'html',`
` valuePrepareFunction: (value) => { return this._sanitizer.bypassSecurityTrustHtml(this.input); },`
` filter: false`
` },`
` }`
`};`
...
`public input: string = '/input>';`