code: def downgrade():
      """Unapply Change default ``pool_slots`` to ``1``"""
      conn = op.get_bind()
      if conn.dialect.name == "mssql":
          inspector = sa.inspect(conn.engine)
          columns = inspector.get_columns("task_instance")
          for col in columns:
              if (
                  col["name"] == "pool_slots"
                  and col["default"] == "('1')"
              ):
                  with op.batch_alter_table(
                      "task_instance", schema=None
                  ) as batch_op:
                      batch_op.alter_column(
                          "pool_slots",
                          existing_type=sa.Integer,
                          nullable=True,
                          server_default=None,
                      )
      else:
          with op.batch_alter_table(
              "task_instance", schema=None
          ) as batch_op:
              batch_op.alter_column(
                  "pool_slots",
                  existing_type=sa.Integer,
                  nullable=True,
                  server_default=None,
              )
  
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