Check whether the resource at a given path is of a desired type

Hi all. Is there a way to determine if a file is of a certain resource type besides just loading it?
I've implemented an asset browser and I want it only to show SpatialMaterials. I tried ResourceLoader.exists(path, type), but the type doesn't really factor into the method's result. I know I could require users to give materials the .material extension, but I'd like a more elegant solution, if there is any.
Thanks in advance.

static func _iter_over_files(path: String, f: FuncRef, resource_type: String=""):
    var todo := [path]
    # Iterate over the given path (as directory) and any sub-directories that
    # may be found.
    while not todo.empty():
        var curr_dir = todo.pop_back()
        var directory = Directory.new()
        if directory.open(curr_dir) == OK:
            directory.list_dir_begin(true)
            var item = directory.get_next()
            # iterate over items in current directory:
            while item != "":
                var item_path = _join_paths(curr_dir, item)
                if directory.current_is_dir():
                    todo.push_back(item_path)
                else:
                    var correct_type = resource_type == "" or ResourceLoader.exists(item_path, resource_type) # that's not how you do it...
                    print("Checking if resource=%s has type=%s: %s" % [item, resource_type, str(correct_type)])
                    if correct_type:
                        f.call_func(item_path)
                item = directory.get_next()
        else:
            push_error("Unable to access directory '%s'" % curr_dir)