Returns a sorted seq from coll in either ascending or descending order. If ascending is true, the result should contain all items which are > or >= than k. If ascending is false, the result should contain all items which are < or <= than k, e.g. (-sorted-seq-from (sorted-set 1 2 3 4 5) 3 true) => (3 4 5) (-sorted-seq-from (sorted-set 1 2 3 4 5) 3 false) => (3 2 1)