title: Django easy way to create model from a multiple models
body: <p>Given these pseudo-models:</p>
  
  <pre><code>class A(models.Model):
      aa = models.CharField()
      ab = models.CharField()
      # ... many other fields
  
  class B(models.Model):
      ba = models.CharField()
      bb = models.CharField()
      # ... many other fields
  
  class C(models.Model):
      ca = models.CharField()
      cb = models.CharField()
      # ... many other fields
  </code></pre>
  
  <p>Now I have another model which aggregates <strong>SOME</strong> of the above models' properties, like this, think of it as an audit table which stores snapshots:</p>
  
  <pre><code>class Agg(models.Model):
      aa = models.CharField() # from A
      bb = models.CharField() # from B
      ca = models.CharField() # from C
      # ... many other fields from A, B and C
  </code></pre>
  
  <p>When creating an <code>Agg</code> I need to name all of the properties explicitly like the following:</p>
  
  <pre><code>Agg.objects.create(
           aa=a_instance.aa, 
           bb=b_instance.bb, 
           ca=c_instance.ca, # and so on ...
  )
  </code></pre>
  
  <p>This is cumbersome if models have many fields. Is there a better/shorter way of doing this?</p>