code: def downgrade():
      """Unapply Add processor_subdir to DagModel and SerializedDagModel"""
      conn = op.get_bind()
      with op.batch_alter_table("dag", schema=None) as batch_op:
          batch_op.drop_column("processor_subdir")
  
      with op.batch_alter_table(
          "serialized_dag", schema=None
      ) as batch_op:
          batch_op.drop_column("processor_subdir")
  
      with op.batch_alter_table("callback_request") as batch_op:
          batch_op.drop_column("processor_subdir")
          if conn.dialect.name == "mysql":
              batch_op.add_column(
                  sa.Column(
                      "dag_directory",
                      sa.Text(length=1000),
                      nullable=True,
                  )
              )
          else:
              batch_op.add_column(
                  sa.Column(
                      "dag_directory",
                      sa.String(length=1000),
                      nullable=True,
                  )
              )
  
imports: from __future__ import annotations
  import sqlalchemy
  from alembic import op
label_desc: Use image node_id 2 for calling a global function with example usage: downgrade() without return types