def _purge_fields(cls, collection_name, field_names):
        """Removes the fields from all in-memory samples in the collection."""
        if collection_name not in cls._instances:
            return

        for sample in cls._instances[collection_name].values():
            for field_name in field_names:
                sample._doc._data.pop(field_name, None)
Removes the fields from all in-memory samples in the collection.
fiftyone/core/singletons.py