Is there built-in data structure in clojure supporting both duplicated elements and O(1) removing? -

recently, need implement special set in clojure may have duplicated elements (i.e. multiset), like

#{1 2 3 4 1 2} 

what's more, removing arbitrary element equal assigned value in o(1) time needed well. example, when type

(my-remove #{1 1 2 2 3 4} 2) 

it should return #{1 1 2 3 4} without loop through whole set(or vector).

my question is, there built-in data structure in clojure satisfying these 2 properties. if not, there proper alternative solution implement this? thanks!

a map of values "count" ? (removing value decreasing counter ?)