These containers are direct equivalents of those supplied in the STL. Be compatible with C++ 03 but implement as many of the C++ 11/14/17/20/23 additions as possible. Add other useful components that ...

Both ‘key’ and ‘string’ must be a bytes-like object (bytes, bytearray…). I assume that the docs decided to use 'data' to remove this ambiguity as 'data' is more common for bytes-like objects. cc ...