Create a new OrderedMap.

Create a new OrderedMap and populate from a list of key-value pairs.

the key-value pair type, for initializing from a list of key-value pairs, or for looping entries in the same order.

the OrderedMap type, has similar operations as the default map, but maintained the keys order of inserted; similar to map, all single key operations (Get/Set/Delete) runs at O(1).