Check if Key exists in Associative Array using D language.

[BoQsc via Digitalmars-d-learn]

I've found [std.algorithm: canFind][1] to be useful on a 
**regular arrays**.

I'd like to know if there is similar function: that can check if 
a **key** inside a [Associative Array][2] can be found.

[1]:https://dlang.org/phobos/std_algorithm_searching.html#.canFind
[2]:https://dlang.org/spec/hash-map.html