How to get mavextract.py to output a specific mode?

How do you use mavextract.py to output a given mode? For example, I have a custom mode, mode 50. This statement:

mavextract.py --condition MODE==50 00000035.BIN

doesn’t work.

That condition has to be a valid Python expression typically referencing
fields in a message - which your condition there is not doing. That
would be more appropriate for mavlogdump.py, however.

pbarker@bluebottle:/tmp/spare$ ls
000019.BIN
pbarker@bluebottle:/tmp/spare$ ls -l
total 8404
-rw-r–r-- 1 pbarker pbarker 8601800 Aug 14 10:09 000019.BIN
pbarker@bluebottle:/tmp/spare$ mavlogdump.py 000019.BIN --t MODE
2017-06-30 04:37:16.12: MODE {TimeUS : 734397930, Mode : 5, ModeNum : 5,
Rsn : 17}
2017-06-30 04:37:28.56: MODE {TimeUS : 746839556, Mode : 6, ModeNum : 6,
Rsn : 1}
2017-06-30 04:37:42.48: MODE {TimeUS : 760753106, Mode : 5, ModeNum : 5,
Rsn : 17}
2017-06-30 04:37:54.26: MODE {TimeUS : 772538091, Mode : 6, ModeNum : 6,
Rsn : 1}
2017-06-30 04:38:39.85: MODE {TimeUS : 818123743, Mode : 5, ModeNum : 5,
Rsn : 1}
2017-06-30 04:43:10.22: MODE {TimeUS : 1088495627, Mode : 9, ModeNum : 9,
Rsn : 4}
pbarker@bluebottle:/tmp/spare$ ~/rc/pymavlink/tools/mavextract.py
–mode=RTL 000019.BIN
Processing 000019.BIN
Creating RTL1.bin
Creating RTL2.bin
pbarker@bluebottle:/tmp/spare$

Peter