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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 _generate_union_class_vars(self, data_type):
 """ Adds a _catch_all_ attribute to each class. Also, adds a placeholder attribute for the construction of union members of void type. """

        lineno = self.lineno
        if data_type.catch_all_field:
            self.emit("_catch_all = '%s'" % data_type.catch_all_field.name)
        elif not data_type.parent_type:
            self.emit('_catch_all = None')

        # Generate stubs for class variables so that IDEs like PyCharms have an
        # easier time detecting their existence.
        for field in data_type.fields:
            if is_void_type(field.data_type):
                field_name = fmt_var(field.name)
                self.emit('# Attribute is overwritten below the class definition')
                self.emit('{} = None'.format(field_name))

        if lineno != self.lineno:
            self.emit()