Description
Most functions in the xarray interface allow kwargs, which are passed to apply_ufunc or downstream to control behaviour of other stats functions called as intermediate steps of the one currently being called (e.g. hist/kde in hdi).
For functions that take **kwargs and pass them downstream it is generally not a good idea to check kwargs, as the downstream functions might change behaviour from time to time, but functions that consume those kwargs we should make sure we check there are no leftover kwargs.
As of now, there are several places where we take elements from kwargs by name and silently ignore extra keys in kwargs. For example both dims="draw" and dim="draw" work without error or warning in hdi, but dims is silently ignored (you can check in the output that both chain, draw have been reduced, the default sample_dims in rcParams)
