code: def namespace(self, namespace, to=None):
          
          fields = get_apphook_field_names(self.model)
          if not fields:
              raise ValueError(
                  ugettext(
                      'Can\'t find any relation to an ApphookConfig model in {0}'
                  ).format(self.model.__name__)
              )
          if to and to not in fields:
              raise ValueError(
                  ugettext(
                      'Can\'t find relation to ApphookConfig model named '
                      '"{0}" in "{1}"'
                  ).format(to, self.model.__name__)
              )
          if len(fields) > 1 and to not in fields:
              raise ValueError(
                  ugettext(
                      '"{0}" has {1} relations to an ApphookConfig model.'
                      ' Please, specify which one to use in argument "to".'
                      ' Choices are: {2}'
                  ).format(
                      self.model.__name__, len(fields), ', '.join(fields)
                  )
              )
          else:
              if not to:
                  to = fields[0]
  
          lookup = '{0}__namespace'.format(to)
          kwargs = {lookup: namespace}
          return self.filter(**kwargs)
docs: Filter by namespace. Try to guess which field to use in lookup.
          Accept 'to' argument if you need to specify.