MapSource

Return all key-value pairs whose keys start with the given prefix (using dot-separated paths).

Look up a single key and return its value with provenance, or None if absent.

Apply a key transformation before lookup. The mapper transforms the requested key before it is passed to the underlying source.

Compose this source with a fallback. Keys are looked up in this source first; if absent, the fallback is consulted. Provenance tracks the actual providing source.

Compose this source with a fallback. This source is consulted first; if it returns None, the fallback is tried.

Prepend a prefix to all key lookups. For example, source.prefix("db").get("host") looks up "db.host" in the underlying source.

An iterator over the names of all the elements of this product.

An iterator over all the elements of this product.