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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 variables(self):
 """ Display a list of templatable variables present in the file. Templating is accomplished by creating a bracketed object in the same way that Python performs `string formatting`_. The editor is able to replace the placeholder value of the template. Integer templates are positional arguments. .. _string formatting: https://docs.python.org/3.6/library/string.html """

        string = str(self)
        constants = [match[1:-1] for match in re.findall('{{[A-z0-9]}}', string)]
        variables = re.findall('{[A-z0-9]*}', string)
        return sorted(set(variables).difference(constants))