code: def _get_time(header, keys, name):
          
          for key in keys:
              try:
                  return _to_timestamp(header.pop(key))
              except KeyError:
                  continue
          raise _UnsupportedOperation(name)
docs: Get time from header
  
          Args:
              header (dict): Object header.
              keys (tuple of str): Header keys.
              name (str): Method name.
  
          Returns:
              float: The number of seconds since the epoch