(Draft)

First in, first out key list that can remove a key from anywhere on the list.

Use for a priority list where some members may cancel participation before they are popped off the list.

Use first() for next in line. Use remove(key) to remove the first after use (it is not automatic), or any key you want to remove from the list for any reason.

Additional functions to count the keys, check existance, and iterate keys in forward or reverse order of declaration.

Uses a linked list. Contains no interation and operates at a fixed cost at any scale.

Depending on the Bytes32Set.