Create an Item with themes¶

import json
from datetime import datetime, timezone

import pystac
from pystac.extensions.themes import Theme, ThemeConcept, ThemesExtension

item = pystac.Item(
    id="example-climate-resource",
    geometry=None,
    bbox=None,
    datetime=datetime(2026, 1, 1, tzinfo=timezone.utc),
    properties={},
)
theme = Theme(
    scheme="https://example.com/themes",
    concepts=[
        ThemeConcept(
            id="climate",
            title="Climate",
            description="Climate-related resources",
            url="https://example.com/concepts/climate",
        )
    ],
)
extension = ThemesExtension.ext(item, add_if_missing=True)
extension.apply([theme])

serialized = item.to_dict()
assert ThemesExtension.get_schema_uri() in serialized["stac_extensions"]
assert serialized["properties"]["themes"] == [theme.to_dict()]

restored_item = pystac.Item.from_dict(json.loads(json.dumps(serialized)))
restored_themes = ThemesExtension.ext(restored_item).themes
assert restored_themes is not None
assert restored_themes[0].concepts[0].id == "climate"