def get(self, id, pk='id', deleted=False):
        try:
            if pk == 'id':
                id = int(id)
            if deleted:
                spec = {pk: id}
            else:
                spec = {pk: id, 'data': {'$exists': 1}}
            fields = {'_id': 0}
            row = self.db.docs.find_one(spec, fields)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return Document(**row)
        raise NotFoundError('%s %s not found' % (pk, id))
def add_handles(self, model, forward_handle, backward_handle):
        """
        Add handles to all non-container layers in the model.
        Recursively for non-container layers
        """
        handles_list = []
        model_children = list(model.children())
        if model_children:
            for child in model_children:
                handles_list.extend(self.add_handles(child, forward_handle, backward_handle))
        else:  # leaves
            handles_list.append(model.register_forward_hook(forward_handle))
            handles_list.append(model.register_backward_hook(backward_handle))
        return handles_list