def property_schema(self, key):
        """
        Lookup the schema for a specific property.

        """
        schema = self.__class__.SCHEMA

        # first try plain properties
        plain_schema = schema.get("properties", {}).get(key)
        if plain_schema is not None:
            return plain_schema
        # then try pattern properties
        pattern_properties = schema.get("patternProperties", {})
        for pattern, pattern_schema in pattern_properties.items():
            if match(pattern, key):
                return pattern_schema
        # finally try additional properties (defaults to true per JSON Schema)
        return schema.get("additionalProperties", True)
Lookup the schema for a specific property.