Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

I found that when I use ModelSerializer, if I set a field in ModelSerializer which is duplicate in model. Then ModelSerializer 's exclude attribute won't work well. It still return the exclude fields.

I traced down the code, and found that it failed because ModelSerializer.get_field_names exclude fields by using list. Since I have set the field in the ModelSerializer, there are two fields name in the list returned by ModelSerializer.get_default_field_names.

django model I except to have

class Car(models.Model):
    name = models.CharField(max_length=128)
    username = models.CharField(max_length=128)

serializar I have

class VersionModelSerializer(serializers.ModelSerializer):
    username = fields.IntegerField(validators=my_validator)

    class Meta:
        model = models.Car
        exclude = ('username')

Expected behavior

Excepted to return data like

{
    "name": "car_name"
}

Actual behavior

but username exists in the response like

{
    "name": "car_name",
    "username": "username"
}

according to the reason I explain above, I think ModelSerializer.get_field_names should use set instead of list to exclude fields.