How to replace brackets in Lua using math.gsub?
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I have a function which is used to replace some words with a few characters or numbers. I am using `string.gsub()` function in this way:

    string.gsub(line, "[0-9%a%s/,-]+", "\t")

This works very good with strings with numbers, letters, spaces, `,`, and `/`. I also would like to replace brackets like `(` and `)`. But simply inserting `()` to my pattern doesn't work. I have also tried with `%(` and `%)` but it wasn't successful. How can I replace brackets in Lua using pattern in `string.gsub()` method?
