<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def import_tables(self, only_tables=None, exclude_tables=None):
 """Imports all data in database tables :param set[str] only_tables: names of tables to be imported :param set[str] exclude_tables: names of tables to be excluded """

        for table in self.tables:
            if only_tables is not None and table.name not in only_tables:
                continue

            if exclude_tables is not None and table.name in exclude_tables:
                continue
            self.import_table(table)