Function find_l2_block_range 

pub fn find_l2_block_range<F>(
    target_l1_block: u64,
    best: u64,
    mix_hash_of: F,
) -> Option<(u64, u64)>
where
    F: Fn(u64) -> Option<B256>,

Binary-search headers to find the block-range that was emitted against the given L1 block. The predicate on each header is l1_block_number_from_mix_hash(header.mix_hash).

Returns (first_block, last_block) inclusive. If no L2 block maps to target_l1_block, returns None.