Function sanakirja::btree::del_no_decr

pub fn del_no_decr<T, K, V, P>(
    txn: &mut T, 
    db: &mut Db_<K, V, P>, 
    key: &K, 
    value: Option<&V>
) -> Result<bool, <T as LoadPage>::Error> where
    T: AllocPage + LoadPage,
    K: Storable + PartialEq<K> + ?Sized,
    V: Storable + PartialEq<V> + ?Sized,
    P: BTreeMutPage<K, V>, 

If value is None, delete the first entry for key from the database, if present. Else, delete the entry for (key, value), if present.