Django filter reversed foreignkey
<p>I have these tables in a django app:</p>

<pre><code>class Order(models.Model):
    ...

class SubOrder1(models.Model):
    order = models.ForeignKey(Order, blank=True, null=True)

class SubOrder2(models.Model):
    order = models.ForeignKey(Order, blank=True, null=True)

...
</code></pre>

<p>How can I write a query on Order which results only the orders which has at least one related SubOrder1 or SubOrder2? I need something like</p>

<pre><code>Order.objects.filter(suborder__count__ge = 1, ...)
</code></pre>

<p>I am using Django = 1.9.2 and Python = 3.4.1</p>