/lib/udev/keymaps/hewlett-packard-tx2 is in udev 175-0ubuntu9.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | 0xC2 media
0xD8 f23 # Toggle touchpad button on tx2 (OFF)
0xD9 f22 # Toggle touchpad button on tx2 (ON)
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