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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 list_tables(self):
        '''
        Load existing tables and their descriptions.

        :return:
        '''
        if not self._tables:
            for table_name in os.listdir(self.db_path):
                self._tables[table_name] = self._load_table(table_name)

        return self._tables.keys()