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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def format_list(self, at_char, user, list_name):
        '''Return formatted HTML for a list.'''
        return '<a href="https://twitter.com/%s/lists/%s">%s%s/%s</a>' \
               % (user, list_name, at_char, user, list_name)