A MultiDict wrapper that decodes returned values to unicode on the fly. Decoding is not applied to assigned values.
The key/value contents are assumed to be str/strs or str/FieldStorages (as is returned by the paste.request.parse_ functions).
Can optionally also decode keys when the decode_keys argument is True.
FieldStorage instances are cloned, and the clone’s filename variable is decoded. Its name variable is decoded when decode_keys is enabled.