Fix sort serialization

The `list` parameter gets only one node, not a list of node.

It's needed in order to do things like `sort((?, office held, president of the US), default)` because with the current serialization we would sort the list with only one element that would be the list of the US presidents.
FIx also first and last serialization
Merge pull request #39 from ProjetPP/fix

Fix sort serialization