Explain how in aggregate() with multiple arguments the "from" keyword can be resolved into a groupby/aggregate sequence by initially grouping by all "from" properties appearing in any argument.
Will probably work only if all "from" chains are compatible, i.e. there exists a "super-chain" so that any from chain is a sub-chain of this super-chain.
1) from A from B from D,from A from C from D works with super-chain from A from B from C from D (B and C can be swapped to get another possible super-chain.
2) from A from B, from B from A won't work