code: def downgrade():
      # ### commands auto generated by Alembic - please adjust! ###
      with op.batch_alter_table("alerts") as batch_op:
          batch_op.add_column(
              sa.Column(
                  "database_id",
                  mysql.INTEGER(),
                  autoincrement=False,
                  nullable=False,
              )
          )
          batch_op.add_column(
              sa.Column("sql", mysql.TEXT(), nullable=True)
          )
          batch_op.drop_constraint("alerts_ibfk_3", type_="foreignkey")
          batch_op.drop_constraint("alerts_ibfk_4", type_="foreignkey")
          batch_op.alter_column(
              "crontab",
              existing_type=mysql.VARCHAR(length=50),
              nullable=True,
          )
          batch_op.drop_column("created_on")
          batch_op.drop_column("created_by_fk")
          batch_op.drop_column("changed_on")
          batch_op.drop_column("changed_by_fk")
  
      op.drop_index(
          op.f("ix_sql_observations_dttm"),
          table_name="sql_observations",
      )
      op.drop_table("sql_observations")
      op.drop_table("sql_observers")
      op.drop_table("alert_validators")
  
imports: import sqlalchemy
  from alembic import op
  from sqlalchemy.dialects import mysql
label_desc: Use image node_id 2 for calling a global function with example usage: downgrade() without return types