Checked in a fix for the python validator.

The second comment is does not make sense:

Using the online validator https://www.jsonschemavalidator.net/ completely invalid

UA JSON is is declared correct:
{
'Type': 4,
'Body': {
'not-a-valid-opcua-field-name': 123
}
}

This is valid because the contents of a Variant allow everything and cannot be checked automatically.
Applications that need to verify the contents of a Variant need to check the Type and apply a custom check based on the Type.