[Python] Jsonschema, validating object keys with a custom function

I am using python-jsonschema for json validation. I have an object with localised texts that are specified inside rfc1766 language code keys as followings:

"Description": {
"en": "English Description",
"sv": "Swedish Description",
"fr": "French Description"
},


I've read in the documentation that I could use the 'format' attribute to check a custom format using a function. So, I wrote a method which takes a string as a parameter and returns True if it is an RFC1766 language string.

@_checks_drafts('rfc1766lang')
def rfc1766lang(instance):
"""some logic, return True if rfc1766"""


However I couldn't find any example on how to apply this to do validation on an object key, not a value.

Is this possible?

I have tried something like below but I couldn't succeed

rfc1766_string_schema_v2 = {
'type': 'object',
'format': 'rfc1766lang',
'additionalProperties': False
}


I know that it would be much easier if I had the json string as follows. However, this is not an option for now.

"Description": [{
"lan": "en",
"text": "Description in English"
}, {
"lan": "sv",
"name": "Description in Swedish"
}]

Continue reading...