code: def to_ufo_master_user_data(self, ufo, master):
      
      for key in master.userData.keys():
          if _user_data_has_no_special_meaning(key):
              ufo.lib[key] = master.userData[key]
  
      # Restore UFO data files. This code assumes that all paths are POSIX paths.
      if UFO_DATA_KEY in master.userData:
          for filename, data in master.userData[UFO_DATA_KEY].items():
              ufo.data[filename] = bytes(data)
docs: Set master-specific user data as Glyphs does.