old_contents: import sqlalchemy as sql
  import migrate
  
  _POLICY_TABLE_NAME = 'policy'
  
  def upgrade(migrate_engine):
      meta = sql.MetaData()
      meta.bind = migrate_engine
  
      policy_table = sql.Table(_POLICY_TABLE_NAME, meta, autoload=True)
  
      # adding new columns
      policy_enabled = sql.Column('enabled', sql.Boolean, nullable=False, default=False)
      policy_table.create_column(policy_enabled)
  
new_contents: import sqlalchemy as sql
  
  _POLICY_TABLE_NAME = 'policy'
  
  def upgrade(migrate_engine):
      meta = sql.MetaData()
      meta.bind = migrate_engine
  
      policy_table = sql.Table(_POLICY_TABLE_NAME, meta, autoload=True)
  
      # adding new columns
      policy_enabled = sql.Column('enabled', sql.Boolean, nullable=False, default=False)
      policy_table.create_column(policy_enabled)
  
subject: remove unused import