Simplest method to check whether unordered_map of unordered_maps contains key

I am using an unordered_map of unordered_maps, such that I can reference an element using the "ulti key" syntax:

my_map[k1][k2].

Is there a convenient way to use the same "multi-key" syntax to check whether an element exists before trying to access it? If not, what is the simplest way?