code: def downgrade():
      bind = op.get_bind()
      session = db.Session(bind=bind)
  
      # remove uuid from position_json
      update_dashboards(session, {})
  
      # remove uuid column
      for table_name in models:
          with op.batch_alter_table(table_name) as batch_op:
              batch_op.drop_constraint(
                  f"uq_{table_name}_uuid", type_="unique"
              )
              batch_op.drop_column("uuid")
  
file_path: superset/superset/migrations/versions/2020-09-28_17-57_b56500de1855_add_uuid_column_to_import_mixin.py
imports: import json
  import os
  from json.decoder import JSONDecodeError
  from uuid import uuid4
  import sqlalchemy
  from alembic import op
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy.orm import load_only
  from sqlalchemy_utils import UUIDType
  from superset import db
  from superset.migrations.shared.utils import assign_uuids
  from superset.utils import core
label_desc: Use image node_id 4 for calling a global function with example usage: downgrade() without return types