Dict.get_and_update

You're seeing just the function get_and_update, go back to Dict module for more information.
Link to this function

get_and_update(dict, key, fun)

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This function is deprecated. Use the Map module for working with maps or the Keyword module for working with keyword lists.

Specs

get_and_update(t(), key(), (value() -> {value(), value()})) :: {value(), t()}