Example 1 NOTE: the ordering by rank:
Rank 0 sends table_0, shard_0 to Rank 1.
Rank 2 sends table_1, shard_0 to Rank 1.
Rank 2 sends table_1, shard_1 to Rank 0
Rank 3 sends table_0, shard_1 to Rank 0
NOTE: table_1 comes first due to its source rank being 'first'
On Rank 0:output_tensor = [
 <table_1, shard_0>, # from rank 2
 <table_0, shard_1> # from rank 3
]
On Rank 1: output_tensor = [
 <table_0, shard_0>, # from rank 0
 <table_1, shard_0> # from rank 2
]