code: def define_tables(cls, metadata):
      dt = Table(
          "dt",
          metadata,
          Column(
              "id",
              Integer,
              primary_key=True,
              test_needs_autoincrement=True,
          ),
          Column("col1", String(20)),
          Column(
              "col2",
              String(20),
              server_default=sa.schema.FetchedValue(),
          ),
          Column(
              "col3",
              String(20),
              sa.schema.FetchedValue(for_update=True),
          ),
          Column(
              "col4",
              String(20),
              sa.schema.FetchedValue(),
              sa.schema.FetchedValue(for_update=True),
          ),
          implicit_returning=False,
      )
  
      dialect_name = testing.db.dialect.name
  
      for ins in (
          sa.DDL(
              "CREATE TRIGGER dt_ins AFTER INSERT ON dt "
              "FOR EACH ROW BEGIN "
              "UPDATE dt SET col2='ins', col4='ins' "
              "WHERE dt.id = NEW.id; END"
          ).execute_if(dialect="sqlite"),
          sa.DDL(
              "CREATE TRIGGER dt_ins ON dt AFTER INSERT AS "
              "UPDATE dt SET col2='ins', col4='ins' "
              "WHERE dt.id IN (SELECT id FROM inserted);"
          ).execute_if(dialect="mssql"),
          sa.DDL(
              "CREATE TRIGGER dt_ins BEFORE INSERT "
              "ON dt "
              "FOR EACH ROW "
              "BEGIN "
              ":NEW.col2 := 'ins'; :NEW.col4 := 'ins'; END;"
          ).execute_if(dialect="oracle"),
          sa.DDL(
              "CREATE TRIGGER dt_ins BEFORE INSERT "
              "ON dt "
              "FOR EACH ROW "
              "EXECUTE PROCEDURE my_func_ins();"
          ).execute_if(dialect="postgresql"),
          sa.DDL(
              "CREATE TRIGGER dt_ins BEFORE INSERT ON dt "
              "FOR EACH ROW BEGIN "
              "SET NEW.col2='ins'; SET NEW.col4='ins'; END"
          ).execute_if(
              callable_=lambda ddl, target, bind, **kw: bind.engine.name
              not in ("oracle", "mssql", "sqlite", "postgresql")
          ),
      ):
          my_func_ins = sa.DDL(
              "CREATE OR REPLACE FUNCTION my_func_ins() "
              "RETURNS TRIGGER AS $$ "
              "BEGIN "
              "NEW.col2 := 'ins'; NEW.col4 := 'ins'; "
              "RETURN NEW; "
              "END; $$ LANGUAGE PLPGSQL"
          ).execute_if(dialect="postgresql")
          event.listen(dt, "after_create", my_func_ins)
  
          event.listen(dt, "after_create", ins)
      if dialect_name == "postgresql":
          event.listen(
              dt, "before_drop", sa.DDL("DROP TRIGGER dt_ins ON dt")
          )
      else:
          event.listen(dt, "before_drop", sa.DDL("DROP TRIGGER dt_ins"))
  
      for up in (
          sa.DDL(
              "CREATE TRIGGER dt_up AFTER UPDATE ON dt "
              "FOR EACH ROW BEGIN "
              "UPDATE dt SET col3='up', col4='up' "
              "WHERE dt.id = OLD.id; END"
          ).execute_if(dialect="sqlite"),
          sa.DDL(
              "CREATE TRIGGER dt_up ON dt AFTER UPDATE AS "
              "UPDATE dt SET col3='up', col4='up' "
              "WHERE dt.id IN (SELECT id FROM deleted);"
          ).execute_if(dialect="mssql"),
          sa.DDL(
              "CREATE TRIGGER dt_up BEFORE UPDATE ON dt "
              "FOR EACH ROW BEGIN "
              ":NEW.col3 := 'up'; :NEW.col4 := 'up'; END;"
          ).execute_if(dialect="oracle"),
          sa.DDL(
              "CREATE TRIGGER dt_up BEFORE UPDATE ON dt "
              "FOR EACH ROW "
              "EXECUTE PROCEDURE my_func_up();"
          ).execute_if(dialect="postgresql"),
          sa.DDL(
              "CREATE TRIGGER dt_up BEFORE UPDATE ON dt "
              "FOR EACH ROW BEGIN "
              "SET NEW.col3='up'; SET NEW.col4='up'; END"
          ).execute_if(
              callable_=lambda ddl, target, bind, **kw: bind.engine.name
              not in ("oracle", "mssql", "sqlite", "postgresql")
          ),
      ):
          my_func_up = sa.DDL(
              "CREATE OR REPLACE FUNCTION my_func_up() "
              "RETURNS TRIGGER AS $$ "
              "BEGIN "
              "NEW.col3 := 'up'; NEW.col4 := 'up'; "
              "RETURN NEW; "
              "END; $$ LANGUAGE PLPGSQL"
          ).execute_if(dialect="postgresql")
          event.listen(dt, "after_create", my_func_up)
  
          event.listen(dt, "after_create", up)
  
      if dialect_name == "postgresql":
          event.listen(
              dt, "before_drop", sa.DDL("DROP TRIGGER dt_up ON dt")
          )
      else:
          event.listen(dt, "before_drop", sa.DDL("DROP TRIGGER dt_up"))
  
imports: import sqlalchemy
  from sqlalchemy import Computed
  from sqlalchemy import event
  from sqlalchemy import Identity
  from sqlalchemy import Integer
  from sqlalchemy import String
  from sqlalchemy import testing
  from sqlalchemy.testing import eq_
  from sqlalchemy.testing import fixtures
  from sqlalchemy.testing.assertsql import assert_engine
  from sqlalchemy.testing.assertsql import CompiledSQL
  from sqlalchemy.testing.assertsql import Conditional
  from sqlalchemy.testing.assertsql import RegexSQL
  from sqlalchemy.testing.entities import BasicEntity
  from sqlalchemy.testing.fixtures import fixture_session
  from sqlalchemy.testing.schema import Column
  from sqlalchemy.testing.schema import Table
label_desc: Use image node_id 1 for calling the TriggerDefaultsTest obj's underlying member method code with example usage: obj.define_tables(cls, metadata) without return types