request: MultiMap

Hello, I would like to request that multimap be added to the data library. As a C++ programmer (and a complete Haskell newbie), I find myself frequently using std::multimap from the STL. However, as I'm moving my programs to Haskell, I'm having to do hacks such as a maps of keys to sets of values. I noticed that DData is under consideration, which has a multiset, so why not a multimap? I would implement it myself, but as I said, I am just learning FP. Thanks, James