I     1 <no description>                                                [text/plain] 
A     2 A.txt                                                           [text/plain]
A     3 <no description>                                     [multipart/alternative]
A     4 ├─>B.txt                                                        [text/plain]
A     5 ├─>C.txt                                                        [text/plain]
A     6 └─>D.txt                                                        [text/plain]
A     7 E.txt                                                           [text/plain]
A     8 <no description>                                     [multipart/alternative]
A     9 ├─>F.txt                                                        [text/plain]
A    10 ├─>G.txt                                                        [text/plain]
A    11 └─>H.txt                                                        [text/plain]
A    12 I.txt                                                           [text/plain]