docs: def _create_plain_field(self, attr, options):
          """Creates the form element."""
          method = self._get_field_method(attr.py_type) or self._create_other_field
          klass, options = method(attr, options)
  
          if attr.is_unique:
              options['validators'].append(validators.UniqueEntityValidator(attr.entity))
  
          return klass, options