token0is guaranteed to be strictly less than
token1by sort order.
uintlog value will be
1for the first pair created,
2for the second, etc. (see allPairs/getPair).
tokenBwith the pool type if it has been created, else
nth pair (
0-indexed) created through the factory, or
0x0000000000000000000000000000000000000000) if not enough pairs have been created yet.
0for the address of the first pair created,
1for the second, etc.
tokenBif one doesn't exist already.