I'm using Nebular Template.

I'm trying to use `<nb-select>`.

I couldn't centralize the control, once it as been inside another tag, `<div class="input-group">`, for example.

How could I centralize the `<nb-select>`, and how could I set 100% of width of this control, and the change has been visible at the control?

```
          <div class="input-group">
              <nb-select selected="0">
                <nb-option value="1">Verint Speech</nb-option>
                <nb-option value="2">Nice IA</nb-option>
              </nb-select>
            </div>

```