code: def maps(self):
          
          if not hasattr(self, '_maps'):
              maps = {}
              maps['tex_symbol'] = {}
              maps['siunitx'] = {}
              maps['value_transforms'] = {
                  '__default__': lambda x: round(x, 2),
              }
              self._maps = maps
          return self._maps
docs: A dictionary of dictionaries.
          Each dictionary defines a map which is used to extend the metadata.
  
          The precise way maps interact with the metadata is defined by `figure.fit._extend_meta`.
          That method should be redefined or extended to suit specific use cases.