Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'level') and self.level is not None:
            _dict['level'] = self.level
        if hasattr(self, 'min_size') and self.min_size is not None:
            _dict['min_size'] = self.min_size
        if hasattr(self, 'max_size') and self.max_size is not None:
            _dict['max_size'] = self.max_size
        if hasattr(self, 'bold') and self.bold is not None:
            _dict['bold'] = self.bold
        if hasattr(self, 'italic') and self.italic is not None:
            _dict['italic'] = self.italic
        if hasattr(self, 'name') and self.name is not None:
            _dict['name'] = self.name
        return _dict