code: def _load_assembly_mapping_data(filename):
          
          try:
              assembly_mapping_data = {}
  
              with tarfile.open(filename, "r") as tar:
                  # http://stackoverflow.com/a/2018576
                  for member in tar.getmembers():
                      if ".json" in member.name:
                          with tar.extractfile(member) as tar_file:
                              tar_bytes = tar_file.read()
                          # https://stackoverflow.com/a/42683509/4727627
                          assembly_mapping_data[member.name.split(".")[0]] = json.loads(
                              tar_bytes.decode("utf-8")
                          )
  
              return assembly_mapping_data
          except Exception as err:
              print(err)
              return None
docs: Load assembly mapping data.
  
          Parameters
          ----------
          filename : str
              path to compressed archive with assembly mapping data
  
          Returns
          -------
          assembly_mapping_data : dict
              dict of assembly maps if loading was successful, else None
  
          Notes
          -----
          Keys of returned dict are chromosomes and values are the corresponding assembly map.