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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 telephone(self, mask: str = '', placeholder: str = '#') -> str: """Generate a random phone number. :param mask: Mask for formatting number. :param placeholder: A placeholder for a mask (default is #). :return: Phone number. :Example: +7-(963)-409-11-22. """

        if not mask:
            code = self.random.choice(CALLING_CODES)
            default = '{}-(###)-###-####'.format(code)
            masks = self._data.get('telephone_fmt', [default])
            mask = self.random.choice(masks)

        return self.random.custom_code(mask=mask, digit=placeholder)