code: def _validate(self, schema):
          
          if isinstance(schema, _str_type):
              schema = self.validator.schema_registry.get(schema, schema)
  
          if schema is None:
              raise SchemaError(errors.SCHEMA_ERROR_MISSING)
  
          schema = copy(schema)
          for field in schema:
              if isinstance(schema[field], _str_type):
                  schema[field] = rules_set_registry.get(schema[field],
                                                         schema[field])
  
          if not self.schema_validator(schema, normalize=False):
              raise SchemaError(self.schema_validator.errors)
docs: Validates a schema that defines rules against supported rules.
  
          :param schema: The schema to be validated as a legal cerberus schema
                         according to the rules of this Validator object.