human
Solve the following python programming problem given the following code:
@ classmethod 
def define_tables(cls, metadata) : 
    testtable = Table ('testtable', metadata, Column ('id', Integer, primary_key = True), Column ('data', String (30))) 
    @ sa.event.listens_for (testtable, 'after_create') 
    def insert_data(target, connection, **kw) : 
        connection.execute (target.insert (), { 
            'id' : 89, 
            'data' : 'd1', 
}) 
materialized_view = sa.DDL ('CREATE MATERIALIZED VIEW test_mview AS SELECT * FROM testtable') 
    plain_view = sa.DDL ('CREATE VIEW test_regview AS SELECT * FROM testtable') 
    sa.event.listen (testtable, 'after_create', metadata) 
    sa.event.listen (testtable, 'after_create', materialized_view) 
    sa.event.listen (testtable, 'before_drop', sa.DDL ('DROP MATERIALIZED VIEW test_mview')) 
    sa.event.listen (testtable, 'before_drop', sa.DDL ('DROP VIEW test_regview')) 

    
    

    Fix the buggy line: sa.event.listen (testtable, 'after_create', metadata)
assistant
#Here is Python code to fix the buggy line: sa.

sa.event.listen (testtable, 'after_create', plain_view)