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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _merge_user_attrs(self, attrs_backend, attrs_out, backend_name):
 """ merge attributes from one backend search to the attributes dict output """

        for attr in attrs_backend:
            if attr in self.attributes.backend_attributes[backend_name]:
                attrid = self.attributes.backend_attributes[backend_name][attr]
                if attrid not in attrs_out:
                    attrs_out[attrid] = attrs_backend[attr]