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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 get_username(self):
 """Get a username formatted for a specific token version."""

        _from = self.auth_context['from']
        if self.token_version == 1:
            return '{0}'.format(_from)
        elif self.token_version == 2:
            _user_type = self.auth_context['user_type']
            return '{0}/{1}/{2}'.format(
                self.token_version,
                _user_type,
                _from
            )