docs: def get_meta(self, key=None):
          """Get metadata value for collection."""
          if self.is_fake:
              return {}
  
          if key == "tag":
              return self.tag
          elif key is None:
              ret = {}
              for key in self.journal.info.keys():
                  ret[key] = self.meta_mappings.map_get(self.journal.info, key)[1]
              return ret
          else:
              key, value = self.meta_mappings.map_get(self.journal.info, key)
              return value