docs: def format_field(self, value, spec):
          """
          Provide the additional formatters for localization.
          """
  
          if spec.startswith('date:'):
              _, format_ = spec.split(':', 1)
              return self.format_date(value, format_)
          elif spec.startswith('datetime:'):
              _, format_ = spec.split(':', 1)
              return self.format_datetime(value, format_)
          elif spec == 'number':
              return self.format_number(value)
          else:
              return super(I18nFormatter, self).format_field(value, spec)