def _decode_address_list_field(address_list):
 if (not address_list):
  return None
 if (len(address_list) == 1):
  return _decode_and_join_header(address_list[0])
 else:
  return map(_decode_and_join_header, address_list)

def _decode_address_list_field ( address_list ) : if ( not address_list ) : return None if ( len ( address_list ) == 1 ) : return _decode_and_join_header ( address_list [ 0 ] ) else : return map ( _decode_and_join_header , address_list )
helper function to decode address lists .