/usr/share/doc/gtrayicon/examples/sample.menu is in gtrayicon 1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | #### Menu types ####################################################
#
#   [main] is a special menu. Items here will appear in main menu
#   [my menu] is a normal submenu with name "my menu"
#
#### Items #########################################################
#
#   Each item can have an icon, just use this rule (without spaces
#   between the coma.
#
#     item = command,icon
#
#   If the command includes a coma, escape it with '\,'
#     item = my\, command,icon
#
#   If no icon is defined, follow this rule: 
#     item = command
#
# Example:
#
# Main Menu:
#   Item 1 (with icon 1)
#   Item 2 (without icon)
#   Submenu 1:
#     Item 3 (without icon)
#     Item 4 (with icon 2)
#
[main]
Item 1 = command,/path/icon/1
Item 2 = command
[Submenu 1]
Item 3 = command
Item 4 = command,/path/icon/2
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