{ "keys": ["tab"], "command": "insert_best_completion",
"args": {"default": "\t", "exact": true} },
{ "keys": ["tab"], "command": "insert_best_completion",
"args": {"default": "\t", "exact": false},
"context": [{
"key": "setting.tab_completion",
"operator": "equal",
"operand": true }] },
{ "keys": ["tab"], "command": "reindent",
... etc ...