Pylint and mongoengine's data model

Hi there,

With latest pylint update the lint fail on the documents and the fields (whereas it doesn't fail for Django ORM for instance). Here is a way to reproduce:

# in module.py
import mongoengine

class Doc(mongoengine.Document):

    string_field = mongoengine.StringField()
    dict_field = mongoengine.DictField()
    list_field = mongoengine.ListField()

    def do_stuff(self):
        for element in self.list_field:
            print element
        return self.string_field[0:7] in self.dict_field

# in shell
$ pip install mongoengine==0.10.6 pylint=1.5.5
$ pylint module.py -r no
E: 10,18: Non-iterable value self.list_field is used in an iterating context (not-an-iterable)
E:  9,41: Value 'self.dict_field' doesn't support membership test (unsupported-membership-test)
E:  9,15: Value 'self.string_field' is unsubscriptable (unsubscriptable-object)

Any idea how to fix this?

Start by reproducing the reported diagnostics with the module.py example and the pinned mongoengine and pylint versions from the issue. Trace how MongoEngine document fields are exposed to Pylint, then verify the example no longer reports the three listed errors.