gistfile1.txt

class Document(ModelBase):
    links_to_this = models.ManyToManyField('self', related_name='this_links_to',
                                           symmetrical=False, through='DocumentLink')

class DocumentLink(ModelBase):
    linked_from = models.ForeignKey(Document, related_name='documentlink_from_set')
    linked_to = models.ForeignKey(Document, related_name='documentlink_to_set')
    type = models.CharField(max_length=16)