jsonschema validators using more than one instance

gistfile1.txt

class ReductionParameters:
    _validators = {'twoone': '_validate_two_using_one'}

    def __init__(self, reduction_parameters, schema):
        self._parameters = reduction_parameters
        self._schema = schema
        self._json_validator = None
        self._initialize_json_validator()

    def _validate_two_using_one(self, validator, value, instance, schema):
        one = self._parameters['one']
        if one + instance < value:
            raise ValidationError(f'{instance} is not enough')

    def _initialize_json_validator(self):
        all_validators = dict(Draft7Validator.VALIDATORS)
        for keyword, function_name in self._validators.items():
            function = getattr(self, function_name)  # this is the key. "self" is not present in "function"'s signature
            all_validators[keyword] = function
        self._json_validator = validators.create(meta_schema=Draft7Validator.META_SCHEMA, validators=all_validators)

    def validate(self):
        jsonschema.validate(self._parameters, self._schema, cls=self._json_validator)


schema = r"""{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "one": {
      "type": "number"
    },
    "two": {
      "type": "number",
      "twoone": 42
    }
  }
}
"""
instance = {"one": 1, "two": 1}
redparms = ReductionParameters(instance, json.loads(schema))
redparms.validate()