django 如何再admin界面增加功能

需求：再admin界面的基础 上增加一个授予用户权限的表单，使用Useradmin中一样的授权表单。

from django.contrib import admin
from django import forms
class PermissionForm(forms.ModelForm):
    user_list = forms.MultipleChoiceField(
        choices=(),
        widget=admin.widgets.FilteredSelectMultiple("user_list", False),
        label="grant user permission",
        required=False,
    )

    class Meta:
        fields = ("user_list",)//再页面上增加一个字段

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields["user_list"].choices = self.get_user_list(kwargs["instance"].data_owner)
        self.fields["user_list"].initial = self.get_exit_user_list(kwargs["instance"])

    def get_user_list(self, data_owner):
    //获取所有用户
        return [(i.username, i.username) for i in _User.objects.filter(~Q(username=data_owner)).all()]

    def get_exit_user_list(self, obj):
    //获取已经授予权限的用户
        return [i.username for i in _User.objects.filter(user_permissions__name=str(obj)).all()]

class SampleBatchAdmin(admin.ModelAdmin):
    model = SampleBatch
    form = PermissionForm