mat select closes when selecting code example

Example: close mat select panel when mouse leaves

<mat-select #matmat placeholder="observers" [formControl]="observers"
                                [(value)]="selectedViewers" multiple> 
                                <div (mouseleave)="matmat.close()">
                                    <mat-option *ngFor="let user of allUsers" [value]="user">{{user.firstName}}
                                    </mat-option>
                                </div>
     </mat-select>