anchor.diff:  -type entity_type() :: '*' |
   oz_worker | od_user | od_group | od_space | od_share |
   od_provider | od_handle_service | od_handle | od_cluster | od_harvester |
  -op_file | op_replica | op_transfer | op_user |
  +op_file | op_replica | op_transfer | op_user | op_group |
   op_space | op_share | op_provider | op_metrics.
   -type entity_id() :: undefined | binary().
   -type aspect() :: atom() | {atom(), atom() | binary()}.
  
positive.code: deserialize_type(<<"op_replica">>, _) -> op_replica;
  deserialize_type(<<"op_transfer">>, _) -> op_transfer;
  deserialize_type(<<"op_user">>, _) -> op_user;
  deserialize_type(<<"op_space">>, _) -> op_space;
  deserialize_type(<<"op_share">>, _) -> op_share;
  deserialize_type(<<"op_provider">>, _) -> op_provider;
  
negative.code: serialize_type(op_replica, _) -> <<"op_replica">>;
  serialize_type(op_transfer, _) -> <<"op_transfer">>;
  serialize_type(op_user, _) -> <<"op_user">>;
  serialize_type(op_group, _) -> <<"op_group">>;
  serialize_type(op_space, _) -> <<"op_space">>;
  serialize_type(op_share, _) -> <<"op_share">>;
  serialize_type(op_provider, _) -> <<"op_provider">>;
  