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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 to_dict(self):
        '''Represents the setup section in form of key-value pairs.

        Returns
        -------
        dict
        '''
        mapping = dict()
        for attr in dir(self):
            if attr.startswith('_'):
                continue
            if not isinstance(getattr(self.__class__, attr), property):
                continue
            try:
                value = getattr(self, attr)
            except AttributeError:
                if attr in self._OPTIONAL_ATTRS:
                    continue
                else:
                    raise AttributeError(
                        'Required attribute "{0}" does not exist on '
                        'instance of type "{1}.'.format(
                            attr, self.__class__.__name__
                        )
                    )
            mapping[attr] = value
        return mapping