code: def downgrade():
      pass
  
imports: import re
  from alembic import op
  from sqlalchemy import Column, ForeignKey, Integer, orm, Sequence, String, Table, UniqueConstraint
  from sqlalchemy.exc import SQLAlchemyError
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy.orm import backref, relationship
label_desc: Use image node_id 2 for calling a global function with example usage: downgrade() without return types