docs: def delete_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')
  
      rm = aliased(ResourceAttrMap, name='rm')
  
      log.info("Trying to delete attribute map. %s -> %s", resource_attr_a, resource_attr_b)
      mapping = db.DBSession.query(rm).filter(
                               rm.resource_attr_id_a == resource_attr_a,
                               rm.resource_attr_id_b == resource_attr_b).first()
  
      if mapping is not None:
          log.info("Deleting attribute map. %s -> %s", resource_attr_a, resource_attr_b)
          db.DBSession.delete(mapping)
          db.DBSession.flush()
  
      return 'OK'