I'm playing around with MongoEngine and i just can't find the way querying ReferenceFields

Class Foo(Document)
    bar = ReferenceField(Bar)
    ...

Class Bar(Document)
    value =IntField()
    ...

bars = Bar.objects.filter(value__lt=1000)

Django:

foos = Foo.objects.filter(bar__in=bars)

MongoEngine : ?

Is there a way to achieve this ?

Thanks in advance,

django mongodb reference
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