Function header_rank 

pub fn header_rank(
    module: &PoWModule,
    header: &Header,
) -> Result<(BigUint, BigUint, BigUint)>

Verify provided header is valid for provided PoW module and compute its rank. Returns next mine difficulty, along with the computed rank.

Header’s rank is the tuple of its squared mining target distance from max 32 bytes int, along with its squared RandomX hash number distance from max 32 bytes int. Genesis block has rank (0, 0).