ForEach.not_empty attribute not intuitive; requires workaround

[camflint]

I have a custom schema that looks like the following.

class NewOrderSchema(Schema):
    customer_id = CustomerEntity()
    order_items = ForEach(OrderItemSchema(), if_missing=NoDefault, not_empty=True)
    payment_method_id = Int(min=0, if_empty=0)
    status_id = Int(min=0, if_empty=0)
    notes = String(if_empty='')
    return_url = String(if_empty='/')

The problematic line is this one:

    order_items = ForEach(OrderItemSchema(), if_missing=NoDefault, not_empty=True)

The intent I'm trying to express in the schema is that I should NOT receive an empty list of nested OrderItemSchemas.

I find that in order for this to work, I must specify the if_missing=NoDefault keyword argument in addition to not_empty=True. It took me a long time to figure this out, since I assumed that passing not_empty=True to ForEach() would be sufficient.

Is this behavior intended? If so, could we document it better?