I have a custom field inside a FormField inside a FieldList: **locations**

```
class LocationForm(Form):
    id = HiddenField('id')
    title = StringField(_l('Title'), [Required()])
    location = CoordinatesField(_l('Coordinates'))

class ProjectForm(Form):
    title = StringField(_l('Title'))
    manager = StringField(_l('Manager'))
    description = StringField(_l('Description'))
    locations = FieldList(FormField(LocationForm), min_entries=1)

```

This form when submited is saved to an object like this:

```
document = {
    'title': unicode,
    'description': unicode,
    'manager': unicode,
    'locations': [{
        'id': uuid.UUID,
        'title': unicode,
        'location': {'coordinates':[float], 'text':unicode}
        }],
    }

```

When I try to load the data in to the form for a GET handler, 
everything **but the locations** loads fine:

```
f = form(MultiDict(document))
f.locations.data
>> {'id':'','title':'','location':''}

```

I did some debugging and found that WTForms while loading the document's data in to the form searches for 'locations-0-location' but MultiDict() but that keys doesn't exists. MultiDict doesn't convert a list of dictionaries to the key 'locations-i-...'.

What is the right way to make a WTForm for such a nested data structure?