function in datepicker angular code example

Example: material datepicker

<mat-form-field class="example-full-width" appearance="fill">
  <mat-label>Choose a date</mat-label>
  <input matInput [matDatepicker]="picker">
  <mat-datepicker #picker></mat-datepicker>
</mat-form-field>
<button mat-raised-button (click)="picker.open()">Open</button>