bind_map missing methods compared to native dicts

[kenoslund-google]

When using bind_map from stl_bind.hpp, there are several standard (and widely used) methods that are missing compared to native dictionaries:

>>> print(set(dir({})) - set(dir(my_bound_map)))
{'values', 'popitem', 'get', 'pop', 'copy', 'fromkeys', 'update', 'keys', 'clear', 'setdefault'}

In particular, values, keys and clear are pretty widely used. Is there a reason these are missing? Could they be added? keys would probably be pretty trivial to implement with make_key_iterator. It doesn't look like an equivalent for iter.second exists, but presumably would be pretty simple to add following the same pattern as make_key_iterator. clear should be trivial too.

[Skylion007]

@kenoslund-google Just noone has bothered to implement them. PR welcome on this front with relevant tests.

[bmerry]

I ran into this too, so I've written #3271 to add make_value_iterator, after which it should be very easy to add keys and values.

[bmerry]

Pybind 11 2.8.0 now has keys and values.