Django models definition ordering
Do you really need that method that returns all instances of model1 that have that foreign key? You can use the related field manager from model2 to achieve that. Model2.field_in_model1_set.all() ?
For example, I have 2 models: Model1 and Model2. Model1 has field ForeignKey(Model2). Model2 has method, that returns all instances of Model1 which has this instance of Model2 as ForeignKey. 
But it doesn't work, because Model2 is defined after Model1 and it knows nothing about Model2. How to solve this problem?