*this is not a BIP39 function**
This function is the function used in `cardano-sl` (and Daedalus) to generate a seed from a given mnemonic list.
https://github.com/input-output-hk/cardano-sl/blob/f5b8073b92b8219ae5fbb038c0ceb4a19502a86b/wallet/src/Pos/Util/BackupPhrase.hs#L59-L65 https://github.com/input-output-hk/cardano-sl/blob/429efc2426c63802ae86789f5b828dcbb42de88a/wallet/src/Pos/Util/Mnemonics.hs#L66-L87