code: def drop_relation(self, relation):
          
          with self.connections.fresh_transaction():
              parent = super(RedshiftAdapter, self)
              return parent.drop_relation(relation)
docs: In Redshift, DROP TABLE ... CASCADE should not be used
          inside a transaction. Redshift doesn't prevent the CASCADE
          part from conflicting with concurrent transactions. If we do
          attempt to drop two tables with CASCADE at once, we'll often
          get the dreaded:
  
              table was dropped by a concurrent transaction
  
          So, we need to lock around calls to the underlying
          drop_relation() function.
  
          https://docs.aws.amazon.com/redshift/latest/dg/r_DROP_TABLE.html