ompressed stream of tar blocks for reading
'r|gz'       open a gzip compressed stream of tar blocks
'r|bz2'      open a bzip2 compressed stream of tar blocks
'r|xz'       open an lzma compressed stream of tar blocks
'w|'         open an uncompressed stream for writing
'w|gz'       open a gzip compressed stream for writing
'w|bz2'      open a bzip2 compressed stream for writing
'w|xz'       open an lzma compressed stream for writing
znothing to open)