Angular 7 Mat datepicker -如何将月份名称从短改为长：

import { MatDateFormats, MAT_DATE_FORMATS } from '@angular/material/core';

const MY_DATE_FORMATS: MatDateFormats = {
  parse: {
    dateInput: 'LL',
  },
  display: {
    dateInput: 'LL',
    monthYearLabel: 'MMMM YYYY',
    dateA11yLabel: 'LL',
    monthYearA11yLabel: 'MMMM YYYY',
  },
};

@Component({
  ...
  providers: [
    { provide: MAT_DATE_FORMATS, useValue: MY_DATE_FORMATS },
  ],
})
export class MyComponent {
  ...
}

<mat-form-field>
  <input matInput [matDatepicker]="picker" placeholder="Choose a date">
  <mat-datepicker-toggle matSuffix [for]="picker"></mat-datepicker-toggle>
  <mat-datepicker #picker></mat-datepicker>
</mat-form-field>