old_contents: from django.db import models
  
  def find_fk(from_model, to_model, foreign_key=None):
      if foreign_key:
          if not isinstance(foreign_key, (str, unicode)):
              foreign_key = foreign_key.attname
          fkeys = filter(lambda x: isinstance(x, models.ForeignKey)
                                   and x.rel.to == to_model
                                   and x.attname in [foreign_key,foreign_key+'_id'],
                         from_model._meta.fields)
      else:
          fkeys = filter(lambda x: isinstance(x, models.ForeignKey)
                                   and x.rel.to == to_model,
                         from_model._meta.fields)
  
      if not fkeys:
          return None
      if len(fkeys) > 1:
          raise ValueError("%s has more than one ForeignKey to %s;"
                           " please specify which one to use."
                           % (from_model, to_model))
      if fkeys[0].attname.endswith("_id"):
          return fkeys[0].attname[:-3]
      else:
          return fkeys[0].attname
  
new_contents: from django.db import models
  
  def find_fk(from_model, to_model, foreign_key=None):
      if foreign_key:
          if not isinstance(foreign_key, (str, unicode)):
              foreign_key = foreign_key.attname
          fkeys = filter(lambda x: isinstance(x, models.ForeignKey)
                                   and x.rel.to._meta.db_table == to_model._meta.db_table
                                   and x.attname in [foreign_key,foreign_key+'_id'],
                         from_model._meta.fields)
      else:
          fkeys = filter(lambda x: isinstance(x, models.ForeignKey)
                                   and x.rel.to == to_model,
                         from_model._meta.fields)
  
      if not fkeys:
          return None
      if len(fkeys) > 1:
          raise ValueError("%s has more than one ForeignKey to %s;"
                           " please specify which one to use."
                           % (from_model, to_model))
      if fkeys[0].attname.endswith("_id"):
          return fkeys[0].attname[:-3]
      else:
          return fkeys[0].attname
  
subject: fix problem when using south's orm freezer.