def _prepare(self, model):
if self.order_with_respect_to:
# The app registry will not be ready at this point, so we cannot
# use get_field().
query = self.order_with_respect_to
try:
self.order_with_respect_to = next(
f for f in self._get_fields(reverse=False)
if f.name == query or f.attname == query
)
except StopIteration:
raise FieldDoesNotExist('%s has no field named %r' % (self.object_name, query))
self.ordering = ('_order',)
if not any(isinstance(field, OrderWrt) for field in model._meta.local_fields):
model.add_to_class('_order', OrderWrt())
else:
self.order_with_respect_to = None
if self.pk is None:
if self.parents:
# Promote the first parent link in lieu of adding yet another
# field.
field = next(six.itervalues(self.parents))
# Look for a local field with the same name as the
# first parent link. If a local field has already been
# created, use it instead of promoting the parent
already_created = [fld for fld in self.local_fields if fld.name == field.name]
if already_created:
field = already_created[0]
field.primary_key = True
self.setup_pk(field)
else:
auto = AutoField(verbose_name='ID', primary_key=True,
auto_created=True)
model.add_to_class('id', auto)
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