def _inspect_details(extras)
      details = [self.class.name]
      fields = _members.merge(extras)
      details << Inspect.from_fields(fields) unless fields.empty?
      "#<#{details.join(' ')}>"
    end
def _inspect_details(extras)
      details = [self.class.name]
      fields = _members.merge(extras)
      details << Inspect.from_fields(fields) unless fields.empty?
      "#<#{details.join(' ')}>"
    end
Inspect {State} fields, with extras

 @param extras [Hash] Non-member values to include

 @return [String]
 @api private