See what depends on a given model

def get_all_models():
    import types, inspect
    from django.db.models import loading
    from django.db.models import Model
    apps = loading.get_apps()
    models = set()
    
    for app in apps:
        for attr in dir(app):
            v = getattr(app,attr)
            if inspect.isclass(v) and issubclass(v, Model):
                models.add(v)
    return list(models)

def get_relations(all_models, the_model):
    """
    
    """
    from django.db.models.fields.related import OneToOneField, \
        ManyToManyField, ForeignKey
    
    foreignkeys = []
    one_to_one = []
    many_to_many = []

    for model in all_models:
        if not hasattr(model, '_meta'):
            print "skipping %s" % model
            continue
        for field in model._meta.fields:
            if isinstance(field, OneToOneField): # must come before FK
                to = field.rel.to
                if to not in all_models:
                    raise ValueError
                if issubclass(to, the_model):
                    one_to_one.append((model, to))
            elif isinstance(field, ForeignKey):
                to = field.rel.to
                if to not in all_models:
                    raise ValueError
                if issubclass(to, the_model):
                    foreignkeys.append((model, to))
            elif isinstance(field, ManyToManyField):
                to = field.rel.to
                if to not in all_models:
                    raise ValueError
                if issubclass(to, the_model):
                    many_to_many.append((model, to))
    return foreignkeys, one_to_one, many_to_many