/usr/share/X11/xkb/symbols/mao is in xkb-data 2.10.1-1ubuntu1.
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  | default  partial alphanumeric_keys
xkb_symbols "basic" {
    // Adds the macrons needed for the Maori language to
    // a simple us keyboard layout.
    include "latin"
    name[Group1]="Maori";
    key <AC01>  { [ a,   A,  amacron, Amacron ] };
    key <AD03>  { [ e,   E,  emacron, Emacron ] };
    key <AD08>  { [ i,   I,  imacron, Imacron ] };
    key <AD09>  { [ o,   O,  omacron, Omacron ] };
    key <AD07>  { [ u,   U,  umacron, Umacron ] };
    key <RALT>  { type[Group1]="TWO_LEVEL",
                  [ ISO_Level3_Shift, Multi_key ]   };
    modifier_map Mod5   { <RALT> };
};
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