pystac.extensions.file.MappingObject doesn't work

[jamesvrt]

pystac.extensions.file.MappingObject is broken and/or the docs should not specify to use it. An example:

from pystac.extensions.file import FileExtension, MappingObject

FILE_SIZE = 100
VALUES = {
    1: "Temperate or sub-polar needleleaf forest",
    2: "Sub-polar taiga needleleaf forest",
    3: "Tropical or sub-tropical broadleaf evergreen forest",
...
}

values: List[MappingObject] = [
    MappingObject.create(values=[i], summary=s) for i, s in VALUES.items()
]

file_ext = FileExtension.ext(data_asset, add_if_missing=True)
file_ext.apply(size=FILE_SIZE, values=values)

results in

TypeError: Object of type MappingObject is not JSON serializable

when saving the STAC. The following change is a viable workaround:

values: List[Any] = [
    dict(values=[i], summary=s) for i, s in VALUES.items()
]

[lossyrob]

The fix is to make the values setter here "unbox" the MappingObject in a similar fashion as is done here