Belt_internalBucketsTypetype opt('a) = Js.undefined('a);type container('hash, 'eq, 'c) = {mutable size: int,mutable buckets: array(opt('c)),hash: 'hash,eq: 'eq,};let toOpt: opt('a) => option('a);let return: 'a => opt('a);let emptyOpt: Js.undefined('a);let make: hash:'hash => eq:'eq => hintSize:int => container('hash, 'eq, _);let clear: container(_, _, _) => unit;let isEmpty: container(_, _, _) => bool;