code: def upgrade():
      
      op.drop_constraint('fk_oauth2server_client_user_id_accounts_user',
                         'oauth2server_client', type_='foreignkey')
      op.create_foreign_key(op.f('fk_oauth2server_client_user_id_accounts_user'),
                            'oauth2server_client', 'accounts_user', ['user_id'],
                            ['id'], ondelete='CASCADE')
      op.create_index(op.f('ix_oauth2server_client_user_id'),
                      'oauth2server_client', ['user_id'], unique=False)
      op.drop_constraint('fk_oauth2server_token_user_id_accounts_user',
                         'oauth2server_token', type_='foreignkey')
      op.create_foreign_key(op.f('fk_oauth2server_token_user_id_accounts_user'),
                            'oauth2server_token', 'accounts_user', ['user_id'],
                            ['id'], ondelete='CASCADE')
      op.create_index(op.f('ix_oauth2server_token_user_id'),
                      'oauth2server_token', ['user_id'], unique=False)
      op.drop_constraint('fk_oauth2server_token_client_id_oauth2server_client',
                         'oauth2server_token', type_='foreignkey')
      op.create_foreign_key(
          op.f('fk_oauth2server_token_client_id_oauth2server_client'),
          'oauth2server_token', 'oauth2server_client', ['client_id'],
          ['client_id'], ondelete='CASCADE')
      op.create_index(op.f('ix_oauth2server_token_client_id'),
                      'oauth2server_token', ['client_id'], unique=False)
docs: Upgrade database.