def set_attribute_mapping(resource_attr_a, resource_attr_b, **kwargs):
    """
        Define one resource attribute from one network as being the same as
        that from another network.
    """
    user_id = kwargs.get('user_id')
    ra_1 = get_resource_attribute(resource_attr_a)
    ra_2 = get_resource_attribute(resource_attr_b)

    mapping = ResourceAttrMap(resource_attr_id_a = resource_attr_a,
                             resource_attr_id_b  = resource_attr_b,
                             network_a_id     = ra_1.get_network().id,
                             network_b_id     = ra_2.get_network().id )

    db.DBSession.add(mapping)

    db.DBSession.flush()

    return mapping
Define one resource attribute from one network as being the same as
        that from another network.