code: def downgrade():
      """Unapply Add external executor ID to TI"""
      with op.batch_alter_table(
          "task_instance", schema=None
      ) as batch_op:
          batch_op.drop_column("external_executor_id")
  
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