Get an DataFrame with the positions of the observations.
Parameters:
adata – An AnnData with positions annotation in .obs or
.obsm. Can also be a DataFrame, which is then
treated like the .obs of an AnnData.
position_key – The .obsm key or array-like of .obs keys with the position space
coordinates. Also supports data paths as specified in
get_data_from_key().
Returns:
A DataFrame with the positions of the observations.