Django reverse M2M field (for admin, etc)

reversem2m.py

#This class lets you add the 'other side' of a m2m to a django model.
#Why this is better than just using related_name:
#    -Admin sees it as a real field, gives you the filter_horizontal widget if you ask
#
#Issues:
#    -Probably breaks syncdb (table tries to be created twice)
#
#Non-issues:
#    -Doesn't break south (custom introspection rule makes this field ignored)

#Initially found at
#https://code.djangoproject.com/ticket/897#comment:28

class ReverseManyToManyField(models.ManyToManyField):
    pass
try:
    import south
except ImportError:
    pass
else:
    from south.modelsinspector import add_ignored_fields
    add_ignored_fields([".*\.ReverseManyToManyField$",])

##Example Use
#class Test1(models.Model):
#    tests2 = models.ManyToManyField('Test2', blank=True)
#
#class Test2(models.Model):
#    tests1 = models.ReverseManyToManyField(Test1, through=Test1.tests2.through, blank=True)