* If fails, exit with error message, eg: `Yang error: Sanity check failed: LIST vsDataContainer lacks key statement which MUST be present (See RFC 7950 Sec 7.8.2)`
* Can be disabled by setting `CLICON_CLICON_YANG_LIST_CHECK` to `false`
* empty values of yang type `empty` are encoded as: `{"x":[null]}`
* empty string values are encoded as: `{"x":""}` (changed from `null` in 4.0 and `[null]` in 4.3)
* empty containers are encoded as: `{"x":{}}`
* empty elements in unknown/anydata/anyxml encoded as: `{"x":{}}` (changed from `{"x":null}`)
