code: def _init_metadata(self):
          
          self._min_string_length = None
          self._max_string_length = None
          self._unlock_previous_metadata = {
              'element_id': Id(self.my_osid_object_form._authority,
                               self.my_osid_object_form._namespace,
                               'unlock_previous'),
              'element_label': 'unlock_previous',
              'instructions': 'Indicator to UI on how to treat the previous button',
              'required': False,
              'read_only': False,
              'linked': False,
              'array': False,
              'default_string_values': ['always'],
              'syntax': 'STRING',
              'minimum_string_length': self._min_string_length,
              'maximum_string_length': self._max_string_length,
              'string_set': []
          }
docs: stub