Django:ModelMultipleChoiceField不选择初始选择

from django import forms
from .models import Category

class MyForm(forms.Form):
    categories = forms.ModelMultipleChoiceField(
        queryset=Category.objects.all(),
        widget=forms.CheckboxSelectMultiple,
        initial=lambda: Category.objects.filter(name__in=['Category 1', 'Category 2'])
    )

from django import forms
from .models import Category

class MyForm(forms.Form):
    categories = forms.ModelMultipleChoiceField(
        queryset=Category.objects.all(),
        widget=forms.CheckboxSelectMultiple,
        initial=lambda: Category.objects.filter(name__in=['Category 1', 'Category 2']),
        choices=[(c.id, c.name) for c in Category.objects.filter(name__in=['Category 1', 'Category 2'])]
    )