code: def json_schema(self, **add_keys):
          
          self._json_schema_keys = add_keys
          if self._json_schema is None:
              self._json_schema = self._build_schema(self._schema)
          return self._json_schema
docs: Convert our compact schema representation to the standard, but more verbose,
          JSON Schema standard.
  
          Example JSON schema: http://json-schema.org/examples.html
          Core standard: http://json-schema.org/latest/json-schema-core.html
  
          :param add_keys: Key, default value pairs to add in,
                           e.g. description=""