code: def downgrade():
      pass
  
file_path: superset/superset/migrations/versions/2016-09-22_11-31_eca4694defa7_sqllab_setting_defaults.py
imports: from alembic import op
  from sqlalchemy import Boolean, Column, Integer
  from sqlalchemy.ext.declarative import declarative_base
  from superset import db
label_desc: Use image node_id 2 for calling a global function with example usage: downgrade() without return types