Please help fill the code r'...'

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Assign a regular expression to a new variable mentions_re that matches any mention in a tweet. Your regular expression should use a capturing group to extract the user's username in a mention. Hint: a user mention within a tweet always starts with the @ symbol and is followed by a series of word characters (with no space in between). For more explanations on what a word character is, check out the Note section in Part 1. 192]: mentions_re r