Small, reusable value-conversion functions (e.g. Julian Date <-> ISO 8601, first-of-list, GeoJSON bbox extraction), one Python module per function.
The one-module-per-converter layout means each converter has its own
stable, dereferenceable source URL
(src/converters/<name>.py) -- useful for a data-model document (e.g. a
JSON-LD /vocabulary endpoint) that wants to cite exactly which code a
named conversion resolves to, not just an opaque string.
from converters import CONVERTERS
CONVERTERS["jd_to_isoformat"](2451545.0)Extracted from epntap2cql2, whose
own converters.py re-exports CONVERTERS from here and adds the one
converter that is specific to that service
(get_datalink_url_for_item, which depends on its request context).
Add src/converters/<name>.py defining one function named <name>;
converters.CONVERTERS picks it up automatically at import time — no
separate registration step.