code: def upgrade():
      """Apply Increase maximum length of pool name in ``task_instance`` table to ``256`` characters"""
      with op.batch_alter_table("task_instance") as batch_op:
          batch_op.alter_column(
              "pool", type_=sa.String(256), nullable=False
          )
  
imports: from __future__ import annotations
  import sqlalchemy
  from alembic import op
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade() without return types